CLUSTERING
1) What is Windows Cluster?
Clustering can be best described as a
technology that automatically allows one physical server to take over the tasks
and responsibilities of another physical server that has failed. The obvious
goal behind this, given that all computer hardware and software will eventually
fail, is to ensure that users running mission-critical applications will have
very less downtime when such a failure occurs.
2) What is a Cluster Node?
A cluster node is a server within the cluster, and
it has Windows Server and the Cluster service installed.
3) What is Cluster Service?
The cluster service manages all the activity that
is specific to the cluster. One instance of the cluster service runs on each
node in the cluster. The cluster service does the following
- Manages Cluster Objects and Configurations
- Manages the local restart policy
- Coordinates with other instances of the cluster service in the
cluster
- Handles event notification
- Facilitates communication among other software components
- Performs failover operations
4) What is called a Resource in
Windows cluster?
A resource is a physical or logical entity, which
has below properties:
- Can
be brought online and taken offline
- Can
be managed in the failover cluster
- Can
be owned by only one node at a time
To manage resources, Cluster service communicates
with a resource DLL through Resource Monitor.
5) What are the different states of a
Resource in Windows cluster?
All resources can have following states
- Offline
- Offline_Pending
- Online
- Online_Pending
- Failed
6) What is a Cluster Group?
Conceptually, a cluster group is a
collection of logically grouped cluster resources. It may contain cluster-aware
application services, such as SQL Server Group, File Server.
7) What is Public Network?
A public network (also called as
External network) provides client systems with access to cluster application
services and IP address resources are created on networks that provide clients
access to cluster services.
8) What is Private Network?
A private network (sometimes called as interconnect
or heartbeat connect) is a network that is setup between the nodes of the
cluster and it carries only internal cluster communications.
9) What is Heartbeat in Windows
cluster?
Heartbeats are messages that Cluster Service
regularly sends between the instances of Cluster Service that are on each node
to manage the cluster.
10) What Failover and Failback terms
mean in Windows Cluster?
Failover: Failover is the
process of moving a group of resources from one node to another in the case of
a failure. For example, in a cluster where Microsoft SQL Server is running on
node A and node A fails, SQL Server
automatically fails over to node B of the cluster.
Failback: Failback is the
process of returning a resource or group of resources to the node on which it
was running before it failed over. For example, when node A comes
back online, SQL Server can fail back from node B to
node A.
11) What is Quorum Drive?
This is a logical drive assigned on
the shared disk array specifically for Windows Clustering. Clustering services
write constantly on this drive about the state of the cluster. Corruption or
failure of this drive can fail the entire cluster setup. It also acts as a
voter in the fail over process in case of odd number of nodes.
12) Different types of Quorum Models
supported in windows Server 2008?
- Node Majority – Used when Odd number of nodes are in cluster.
- Node and Disk Majority – Even number of nodes
(but not a multi-site cluster)
- Node and File Share Majority – Even number of nodes, multi-site cluster
- No Majority: Disk Only – This is the traditional MSCS quorum model,
where a shared quorum disk must be online and nodes must be able to
communicate with that disk
13) What is Node Majority model?
This type of quorum is optimal for
clusters having an odd number of nodes. In this configuration, only the nodes
have votes. The shared storage does not have a vote. A majority of votes are
needed to operate the cluster.
14) What is Node and Disk Majority
model?
Nodes and a shared disk get votes.
This configuration allows a loss of half the nodes, providing the disk witness
is available, or over half the nodes are available without the disk witness
being available. This is recommended for even number of nodes in the cluster.
15) What is Node and File Share Majority
model?
This type of quorum is optimal for
clusters having an even number of nodes when a shared witness disk is not an
option. Other characteristics include the following:
- each node and the file share “witness” gets a
vote
- it does not require a shared disk to reach a
quorum
- the file share has no special requirements
- the file share should be located at a third
site, making this type of quorum the best solution for geographically
dispersed clusters
16) What is No Majority: Disk only
mode?
The disk witness must be available to
have quorum, but the number of available nodes doesn’t matter. If you have a
four-node cluster and only one node is available, but the disk witness is
available, you have quorum. If the disk witness isn’t available, then even if all
four nodes are available you can’t have quorum.
17) What I Split Brain situation in
Cluster?
Cluster nodes communicate with each
other over the network (port 3343). When nodes are unable to communicate with
each other, they all assume the resources of the other (unreachable) nodes have
to be brought online. Because the same resource will be brought online on
multiple nodes at the same time, data corruption may occur. These results in a
situation called “Split Brain.”
18) How Spilt Brain situation is resolved?
To prevent Split Brains we need to
bring the cluster resource online on a single node (rather than multiple
nodes). Each of the online node cast vote for majority and the resources
come online on that group which has more votes or has majority. In case of Even
number of nodes Quorum also acts as a voter to eliminate split brain situation.
19) What are the Hardware
requirements for Windows Server Cluster?
Windows Cluster
- Two
windows servers (nodes)
- At
least one shared disk array that supports, either SCSI or fibre channel.
- Each server must have a SCSI or fiber channel
adapter to talk to the shared disk array. The shared disk array cannot use
the SCSI controller used by the local hard disk or CD-ROM.
- Each server must have two PCI network cards
(one for the private connection and one for the public connection)
- 1 IP
Address for Windows virtual cluster name
20) What are the Hardware
requirements for SQL Server Cluster?
- 1 IP
Address for MSDTC service
- 1 IP
Address for SQL Server Active\Passive Instance or 2 IP address for SQL
Server Active\Active Instance
- 1 IP
Address for SQL Server Analysis services (if needed)
21) How many IP Addresses we require
for setting up Active\Passive SQL Server cluster?
- 2
Windows nodes – Public
- 2
Private IP Addresses – Private
- 1 Windows
Virtual Cluster Name
- 1
MSDTC
- 1
SQL Server Virtual Network Name
22) How many IP Addresses we require
for setting up Active\Active SQL Server cluster with Analysis services?
- 2 Windows nodes – Public
- 2 Private IP Addresses – Private
- 1 Windows Virtual Cluster Name
- 1 MSDTC
- 1 SQL Server Virtual Network Name
- 1 SQL Server Analysis Services
23) How do you open a Cluster
Administrator?
Start Menu > Run > Cluadmin.msc
24) What is SQL Server Network Name
(Virtual Name)?
This is the SQL Server Instance name that all
client applications will use to connect to the SQL Server.
25) Different types of SQL Server
Cluster?
- Active\Passive
- Active\Active
26) What is the difference between
Active\Passive and Active\Active cluster?
An Active – Passive cluster is a failover
cluster configured in a way that only one cluster node is active at any given
time. The other node, called as Passive node is always online but in an idle
condition, waiting for a failure of the Active Node, upon which the Passive
Node takes over the SQL Server Services and this becomes the Active Node, the
previous Active Node now being a Passive Node.
An Active – Active cluster
is a failover cluster configured in a way that both the cluster nodes are
active at any given point of time. That is, one Instance of SQL Server is
running on each of the nodes always; when one of the nodes has a failure, both
the Instances run on the only one node until the failed node is brought up
(after fixing the issue that caused the node failure). The instance is then
failed over back to its designated node.
27) Difference between SQLSERVER 2005
and SQLSERVER 2008 Cluster Installation?
In sql2005 we have the option of
installing SQL in remaining nodes from the primary node, But in sql2008 we need
to go separately (Login to the both nodes) for installing SQL cluster
28) Can we change the Quorum settings
after installing the windows cluster?
Yes, we can change the Quorum setting after the
Windows Cluster installation.
29) Is it mandatory to configure
MSDTC in Windows 2008 cluster before installing SQL Server cluster?
No it’s not mandatory to configure
MSDTC service to install SQL Server in Windows 2008 cluster. Installation will
give you a warning but will not stop the installation.
30) What are the Benefits of SQL
Server Cluster?
- Reduces downtime to a bare minimum.
- Permits an automatic response to a failed server or software. No
human intervention is required.
- It allows you to perform upgrades without forcing users off the
system for extended periods of time.
- It allows you to reduce downtime due to routine server, network, or
database maintenance.
- Clustering doesn’t require any servers to be
renamed. So when failover occurs, it is relatively transparent to
end-users.
- Failing back is quick, and can be done whenever the primary is
fixed and put back on-line.
31) What are the Drawbacks of SQL
Server Cluster?
- More expensive than other failover alternatives, such as log
shipping or stand-by servers.
- Requires more set up time than other alternatives.
- Requires more on-going maintenance than other alternatives.
- Requires more experienced DBAs and network administrators.
32) What new functionality does
failover clustering provide in Windows Server 2008?
New validation feature. With this feature, you can
check that your system, storage, and network configuration is suitable for a
cluster.
Support for GUID partition table
(GPT) disks in cluster storage. GPT disks can have partitions larger than two
terabytes and have built-in redundancy in the way partition information is
stored, unlike master boot record (MBR) disks.
33) What happens to a running
Cluster if the quorum disk fails in Windows Server 2008 Cluster?
Cluster continues to work but
failover will not happen in case of any other failure in the active node.
34. What happens to a running
Cluster if the quorum disk fails in Windows Server 2003 Cluster?
In Windows Server 2003, the Quorum
disk resource is required for the Cluster to function. In your example, if
the Quorum disk suddenly became unavailable to the cluster then both nodes
would immediately fail and not be able to restart the cluster service.
35) What are Virtual Servers?
Groups that contain an IP address
resource and a network name resource (along with other resources) are published
to clients on the network under a unique server name. Because these groups
appear as individual servers to clients, they are called virtual servers. Users
access applications or services on a virtual server the same way they access
applications or services on a physical server. They do not need to know that
they are connecting to a cluster and have no knowledge of which node they are
connected to.
36) How do you bring the SQL Server
down?
In the Cluster Administrator, rick click on the SQL
Server Group and from the popup menu item choose Take Offline.
37) How will you add a disk to the
SQL Group cluster?
After adding the shared disk in the storage, we can
add disk to the respective SQL Server Group.
38) What is the maximum number
of nodes in an MNS cluster in Windows Server 2008, Enterprise x64 Edition?
Maximum 16.
39) What does a failover cluster do
in Windows Server 2008?
A failover cluster is a group of
independent computers that work together to increase the availability of
applications and services. The clustered servers (called nodes) are connected
by physical cables and by software. If one of the cluster nodes fails, another
node begins to provide service (a process known as failover). Users experience
a minimum of disruptions in service.
40) What are Services and Application
folder represent?
Services and applications are managed
as single units for configuration and recovery purposes. If a resource depends
on another resource, both resources must be a member of the same service or
application. For example, in a file share resource, the service or application
containing the file share must also contain the disk resource and network
resources (such as the IP address and NetBIOS name) to which clients connect to
access the share. All resources within a service or application must be online
on the same node in the cluster.
41) What kinds of permissions are
required in the active directory to setup the SQL Server cluster objects?
Service account needs create object permissions in
the Active Directory.
42) Why do we keep SQL Services in
manual mode on each of the instance?
SQL Services should always be in manual mode in
case of cluster because these are managed by the Cluster service and it’s taken
online on its respective owner node based on the failover.
43) What is Distributed lock management?
Distributed lock management (DLM):
Distributed lock management (DLM) enables two servers to access the same
physical disk at the same time without corrupting the data. If a device is
updating a particular file or piece of data, the device gets locked so that
another controller can’t seize ownership and overwrite the data. NT does not
currently support DLM, so disks are dedicated to one node or the other.
44) What is “Look Alive”?
LooksAlive: Verifies that the SQL Server service
runs on the online node every 5 seconds by default.
45) What is “IS Alive”?
IsAlive: Verifies that SQL Server accepts
connections by executing sp_server_diagnostics. This health detection logic
determines if a node is down and the passive node then takes over the
production workload.
46 What are SQL Server Cluster aware
services?
- SQL Server Service
- SQL Server Agent Service
- SQL Server Analysis Service
47) What are SQL Server Cluster
unaware services?
- SQL Server Reporting Service
- SQL Server Integration Service
48) What are Validation tests in
Windows Cluster?
Validation test is a mechanism of verifying that
all the components which are participating in the Windows cluster are fine and
failover is happening between the nodes.
49) What are the basics tests done by
the validation tests in Windows Cluster?
- Cluster Configuration tests: Validate important cluster
configuration settings.
- Inventory tests: Provide an inventory of the hardware, software,
and settings (such as network settings) on the servers, and information about
the storage.
- Network tests: Validate that networks are set up correctly for
clustering.
- Storage tests: Validate that the storage on which the failover
cluster depends is behaving correctly and supports the required functions
of the cluster.
- System Configuration tests: Validate that the system software and
configuration settings are compatible across servers.
50) Where the results of validation
tests are stored?
These reports are automatically stored for you in
C:\Windows\Cluster\Reports as MHTML files.
51) Is SQL Server a Load balancing
solution or not?
No, it’s not a Load balancing solution.
52) Will there be any downtime in
Active\Active cluster in case of any failover?
Yes, definitely there will be downtime when SQL
Server failover from one node to another.
53) Can we use other SQL Server
cluster Nodes for reporting purpose as we can do in Logshipping and Database
mirroring?
No it’s not possible in SQL Server Cluster feature.
54) Can we place out Non Critical SQL
Server User Databases on a Clustered Instance on Disks that are not clustered
to Save Money?
No, it’s not possible. SQL Server 2012 and all
previous versions of SQL Server require databases be created on clustered
resources. Internal drives or drives which are not part of the cluster group cannot
hold user databases.
55) Can we configure Tempdb database
on a local drive?
With the introduction of SQL Server 2012 Microsoft
officially supports local disk TempDB in SQL Server cluster configurations.
56) Can we configure Windows cluster
between two servers which are having different hardware and software
configurations?
No it is not possible.
57) What is SMB share?
SMB stands for Server Message Block file server
which can be used as a storage option starting SQL Server 2012 to store system
databases (Master, Model, MSDB, and TempDB), and Database Engine user
databases .
58) How can we check the current
node/host name where SQL Server is running?
Select
serverproperty(‘ComputerNamePhysicalNetBIOS’)
59) How to view the Cluster Nodes
using command line?
C:\Windows\System32>cluster node
--or
C:\Windows\System32>cluster node
/status
60) How to view the status for all
cluster resource groups.
C:\Windows\System32>cluster group
--or
C:\Windows\System32>cluster group
/status
61) How to get a listing of all
available cluster resources?
C:\Windows\System32>cluster
resource
--or
C:\Windows\System32>cluster
resource /status
62) How to failover a service from
one node to another?
C:\Windows\System32>cluster group
"groupname" /move:nodeName
63) What is the difference between SQL
Server clustering methods: - Active/Active - Active/Passive
Active/Active means that both nodes are active and
accessing the shared disk resources, but are running independent instances. When
a node fails, you need to be sure that the remaining node has the resources
available to handle the additional databases that fail over. You can think of
it like this. Node A has 1 database on it, and Node B has 1 database on it.
Node A goes down, the resources fail over to Node B, and now Node B has 2
databases running on it.
In an Active/Passive cluster, you would only have 1
database running on a single node at any given time. Node A is active with 1
DB, Node B is passive with no DBs. Node A goes down, the resources fail over to
Node B. Node B is now active with 1 database running on it.
I'm sure more experienced cluster admins or SQL
admins will savage me for my terminology, but that's it in a nutshell.
64) What is the alive & Looks alive
LooksAlive check:
LooksAlive is a basic
check in which the Cluster service queries the Windows Service Control Manager
to check if the SQL Server service is still running. By default this check
happens every 5 seconds.
Cluster service calls
looksAlive function every 5 seconds and LookAlive function Queries the service
status by using the Windows NT Service Control Manager. When the LooksAlive
test fails ISAlive test is called immediately.
ISalive
Check: A more rigorous IsAlive function is called every 60 second and monitors
the health of the SQL Server by opening up a connection to SQL Server and
issuing “select @@servername” query over the connection. If the checks fail the
online Thread reports this failure to the Cluster Service.
During IsAlive check
the Cluster Service connects to the SQL Server instance with the help of
c:\windows\system32\sqsrvres.dll and runs SELECT @@SERVERNAME against
the instance.
By default,
LooksAlive is fired every 5 seconds and IsAlive is fired every 60 seconds. The
LooksAlive and IsAlive polling intervals can be changed in Cluster
Administrator or failover cluster manager from the advanced tab for the SQL
Server resource or using the cluster.execommand prompt utility.
65)
What is meant by Active – Passive and Active – Active clustering setup?
An Active – Passive cluster is a
failover cluster configured in a way that only one cluster node is active at
any given time. The other node, called as Passive node is always online but in
an idle condition, waiting for a failure of the Active Node, upon which the
Passive Node takes over the SQL Server Services and this becomes the Active
Node, the previous Active Node now being a Passive Node.
An Active – Active cluster is a failover cluster configured in a way that both the cluster
nodes are active at any given point of time. That is, one Instance of SQL
Server is running on each of the nodes always; when one of the nodes has a
failure, both the Instances run on the only one node until the failed node is
brought up (after fixing the issue that caused the node failure). The instance
is then failed over back to its designated node.
66)
List out some of the requirements to setup a SQL Server failover cluster.
Virtual network name for the SQL
Server, Virtual IP address for SQL Server, IP addresses for the Public Network
and Private Network(also referred as Hearbeat) for each node in the failover
cluster, shared drives for SQL Server Data and Log files, Quorum Disk and MSDTC
Disk.
67)
On a Windows Server 2003 Active – Passive failover cluster, how do you find the
node which is active?
Using Cluster Administrator, connect to
the cluster and select the SQL Server cluster. Once you have selected the
SQL Server group, in the right hand side of the console, thecolumn “Owner” gives us the information of the node on which the SQL Server group
is currently active.
68)
How do you open a Cluster Administrator?
From Start -> Run and type CluAdmin (case insensitive) and the Cluster Administrator console is displayed OR you can also go to Start -> All programs -> Administrative Tools -> Cluster Administrator.
From Start -> Run and type CluAdmin (case insensitive) and the Cluster Administrator console is displayed OR you can also go to Start -> All programs -> Administrative Tools -> Cluster Administrator.
69) How will you restart your sqlserver
on cluster without failing over ..?
Choose option ( Take offline and Bring
online option by right clicking node)
70) What will you if want to add a disk to the SQL Group cluster ..?
Need to choose Add Dependancy option after doing that in Cluster administrator tool (or) in Failover Cluster admin tool from 2008 version
71) As a DBA how will you design active/active cluster requirement . (i.e), how will you manage resource if failed over ..?
Please read article from MSDN on this
to have better understanding
72) Steps for failover ..?
Please red MSDN on this with full view
73) Difference between SQLSERVER 2005 and SQLSERVER 2008 Cluster Installation ..?
In sql2005 we have the option of installing sql in remaining nodes from the primary node ., But in sql2008 we need to go seperately(Login to the bith nodes) for installing sql cluster .
74) What is the status of
services on passive node for failover cluster in SQL server?
SQL services will be in manual and
stopped. Cluster service will be in automatic and started mode on both the
nodes.
75) Can you move the resources
after pausing the node?
Yes resources can be moved after
pausing the node. But we can't move them back till the node is paused.
76) Where is the prevent failback
option?
This is the resource group property.
It doesn't allow the resources to move back to the preferred node once the node
is ready to take the connections after failover.
77) How does the failover
happen? What checks are performed to ensure that another node is up?
LooksAlive - The node which host the SQL server resources is
verifed whether this node (server) is up
IsAlive - The node
which host the SQL server resources is verifed whether the SQL service is up or
not. Basically running SELECT @@SERVERNAME
78) What will happen if you try to
start the fultext service on the passive node.
This can be started on both the nodes
as this doesn't have any dependecy on SQL service or any resource which is
possessed by active node.
79) What is Clustering. Briefly define
& explain it ?
Clustering is a technology, which is
used to provide High Availability for mission critical applications. We can
configure cluster by installing MCS (Microsoft cluster service) component from
Add remove programs, which can only available in Enterprise Edition and Data
center edition.
80) Types of Clusters ?
80) Types of Clusters ?
In Windows we can configure two types
of clusters
1. NLB (network
load balancing) cluster for balancing load between servers. This cluster will
not provide any high availability. Usually preferable at edge servers like web
or proxy.
2. Server Cluster: This provides High availability by configuring active-active or active-passive cluster. In 2 node active-passive cluster one node will be active and one node will be stand by. When active server fails the application will FAILOVER to stand by server automatically. When the original server backs we need to FAILBACK the application
2. Server Cluster: This provides High availability by configuring active-active or active-passive cluster. In 2 node active-passive cluster one node will be active and one node will be stand by. When active server fails the application will FAILOVER to stand by server automatically. When the original server backs we need to FAILBACK the application
81) What is Quorum ?
A shared storage need to provide for
all servers which keeps information about clustered application and session
state and is useful in FAILOVER situation. This is very important if Quorum
disk fails entire cluster will fails.
82) Why Quorum is necessary ?
When network problems occur, they can
interfere with communication between cluster nodes. A small set of nodes might
be able to communicate together across a functioning part of a network, but
might not be able to communicate with a different set of nodes in another part
of the network. This can cause serious issues. In this “split” situation, at
least one of the sets of nodes must stop running as a cluster.
To prevent the issues that are caused
by a split in the cluster, the cluster software requires that any set of nodes
running as a cluster must use a voting algorithm to determine whether, at a
given time, that set has quorum. Because a given cluster has a specific set of
nodes and a specific quorum configuration, the cluster will know how many
“votes” constitutes a majority (that is, a quorum). If the number drops below
the majority, the cluster stops running. Nodes will still listen for the
presence of other nodes, in case another node appears again on the network, but
the nodes will not begin to function as a cluster until the quorum exists
again.
For example, in a five node cluster
that is using a node majority, consider what happens if nodes 1, 2, and 3 can
communicate with each other but not with nodes 4 and 5. Nodes 1, 2, and 3
constitute a majority, and they continue running as a cluster. Nodes 4 and 5
are a minority and stop running as a cluster, which prevents the problems of a
“split” situation. If node 3 loses communication with other nodes, all nodes
stop running as a cluster. However, all functioning nodes will continue to
listen for communication, so that when the network begins working again, the
cluster can form and begin to run.
83) Different types of Quorum in Windows server 2008 ?
1.Node Majority - Used when Odd number
of nodes are in cluster.
2.Node and Disk Majority - Even number
of nodes(but not a multi-site cluster)
3.Node and File Share Majority - Even
number of nodes, multi-site cluster
4.Node and File Share Majority - Even
number of nodes, no shared storage
84) Different types of Quorum in
Windows server 2003 ?
Standard Quorum : As mentioned above, a quorum is simply a
configuration database for MSCS, and is stored in the quorum log file. A
standard quorum uses a quorum log file that is located on a disk hosted on a
shared storage interconnect that is accessible by all members of the
cluster.
Standard quorums are available in Windows NT 4.0 Enterprise Edition, Windows 2000 Advanced Server, Windows 2000 Datacenter Server, Windows Server 2003 Enterprise Edition and Windows Server 2003 Datacenter Edition.
Standard quorums are available in Windows NT 4.0 Enterprise Edition, Windows 2000 Advanced Server, Windows 2000 Datacenter Server, Windows Server 2003 Enterprise Edition and Windows Server 2003 Datacenter Edition.
Majority Node Set Quorums : A majority node set (MNS) quorum is a single
quorum resource from a server cluster perspective. However, the data is
actually stored by default on the system disk of each member of the cluster.
The MNS resource takes care to ensure that the cluster configuration data
stored on the MNS is kept consistent across the different disks.
Majority node set quorums are available in Windows Server 2003 Enterprise Edition, and Windows Server 2003 Datacenter Edition.
Majority node set quorums are available in Windows Server 2003 Enterprise Edition, and Windows Server 2003 Datacenter Edition.
85) Explain about each Quorum type ?
Node Majority: Each node that is
available and in communication can vote. The cluster functions only with a
majority of the votes, that is, more than half.
Node and Disk Majority: Each node plus
a designated disk in the cluster storage (the “disk witness”) can vote,
whenever they are available and in communication. The cluster functions only
with a majority of the votes, that is, more than half.
Node and File Share Majority: Each node
plus a designated file share created by the administrator (the “file share
witness”) can vote, whenever they are available and in communication. The
cluster functions only with a majority of the votes, that is, more than half.
No Majority: Disk Only: The cluster has
quorum if one node is available and in communication with a specific disk in
the cluster storage.
86) How is the quorum information located on the system disk of each node kept in synch?
The server cluster infrastructure
ensures that all changes are replicated and updated on all members in a
cluster.
87) Can this method be used to replicate application data as well?
No, that is not possible in this
version of clustering. Only Quorum information is replicated and maintained in
a synchronized state by the clustering infrastructure.
88) Can I convert a standard cluster to an MNS cluster?
Yes. You can use Cluster Administrator
to create a new Majority Node Set resource and then, on the cluster properties
sheet Quorum tab, change the quorum to that Majority Node Set
resource.
89) What is the difference between a geographically dispersed cluster and an MNS cluster?
A geographic cluster refers to a cluster that has nodes in multiple locations, while an MNS-based cluster refers to the type of quorum resources in use. A geographic cluster can use either a shared disk or MNS quorum resource, while an MNS-based cluster can be located in a single site, or span multiple sites.
89) What is the difference between a geographically dispersed cluster and an MNS cluster?
A geographic cluster refers to a cluster that has nodes in multiple locations, while an MNS-based cluster refers to the type of quorum resources in use. A geographic cluster can use either a shared disk or MNS quorum resource, while an MNS-based cluster can be located in a single site, or span multiple sites.
90) What is the maximum number of nodes in an MNS cluster?
Windows Server 2003 supports 8-node
clusters for both Enterprise Edition and Datacenter Edition.
91) Do I need special hardware to use an MNS cluster?
91) Do I need special hardware to use an MNS cluster?
There is nothing inherent in the MNS
architecture that requires any special hardware, other than what is required
for a standard cluster (for example, there must be on the Microsoft Cluster
HCL). However, some situations that use an MNS cluster may have unique
requirements (such as geographic clusters), where data must be replicated in
real time between sites.
92) Does a cluster aware application need to be rewritten to support MNS?
No, using an MNS quorum requires no
change to the application. However, some cluster aware applications expect a
shared disk (for example SQL Server 2000), so while you do not need shared
disks for the quorum, you do need shared disks for the application.
93) Does MNS get rid of the need for shared disks?
It depends on the application. For example,
clustered SQL Server 2000 requires shared disk for data. Remember, MNS only
removes the need for a shared disk quorum.
94) What does a failover cluster do in Windows Server 2008 ?
94) What does a failover cluster do in Windows Server 2008 ?
A failover cluster is a group of
independent computers that work together to increase the availability of
applications and services. The clustered servers (called nodes) are connected
by physical cables and by software. If one of the cluster nodes fails, another
node begins to provide service (a process known as failover). Users experience
a minimum of disruptions in service.
95) What new functionality does failover clustering provide in Windows Server 2008 ?
New validation feature. With this feature, you can check that your system, storage, and network configuration is suitable for a cluster.
95) What new functionality does failover clustering provide in Windows Server 2008 ?
New validation feature. With this feature, you can check that your system, storage, and network configuration is suitable for a cluster.
Support for GUID partition table (GPT)
disks in cluster storage. GPT disks can have partitions larger than two
terabytes and have built-in redundancy in the way partition information is
stored, unlike master boot record (MBR) disks.
96) What happens to a running Cluster if the quorum disk fails in Windows Server 2003 Cluster ?
In Windows Server 2003, the Quorum disk
resource is required for the Clusterto function. In your example, if the Quorum
disk suddenly became unavailableto the cluster then both nodes would
immediately fail and not be able torestart the clussvc.
In that light, the Quorum disk was a
single point of failure in a MicrosoftCluster implementation. However, it was
usually a fairly quick workaround toget the cluster back up and operational.
There are generally two solutionsto that type of problem.
1. Detemrine why the Quorum disk failed
and repair.
2. Reprovision a new LUN, present it to
the cluster, assign it a driveletter and format. Then start one node with the
/FQ switch and throughcluadmin designate the new disk resource as the Quorum.
Then stop andrestart the clussvc normally and then bring online the second
node.
97) What happens to a running Cluster if the quorum disk fails in Windows Server 2008 Cluster ?
Cluster continue to work but failover
will not happen in case of any other failure in the active node.
98) What is Failover clusters in sql
server
As all of us need every service should be 24 into
7 and available every time we need that. So every services provider need to
technically strong. TO overcome this problem new concept comes into picture
that is failover cluster. It is group of independent computers that work
together to increase the availability of applications and services. Here each
clustered server connected by cables and by software. And this clustered
server called nodes. If one cluste
|
r nodes fails then another node begins to work.
It is good technique which is not dependent on single server.
|
99) What is the standard
setting of Lookslive, IsAlive and Pending Timeout?
LooksAlive - 5 sec IsAlive - 30 sec
Pending Timeout - 180 sec
Note- Do not modify Pending Timeout. The value, represented in seconds, is the amount of time the resource in either the Offline Pending or Online Pending states has to resolve its status before the Cluster Service puts the resource in either Offline or Failed status.
100) Can you change failover policy? If Yes then how?
To configure the failover policy, in the Threshold box, enter the number of times the group is allowed to fail over within a set span of hours. In the Period box, enter the set span of hours. For example, if Threshold is set to 10 and Period is set to 6, the Cluster Service fails the group over a maximum of 10 times in a 6-hour period. At the 11th failover in that 6-hour period, the server cluster leaves the group offline. This affects only resources that were failed over; therefore, if the SQL Server resource failed 11 times, it would be left offline, but the IP could be left online.
=========================================================
What is the difference between SQL Server clustering methods: - Active/Active - Active/Passive
Active/Active means that both nodes are active and accessing the shared disk resources, but are running independent instances. When a node fails, you need to be sure that the remaining node has the resources available to handle the additional databases that fail over. You can think of it like this. Node A has 1 database on it, and Node B has 1 database on it. Node A goes down, the resources fail over to Node B, and now Node B has 2 databases running on it.
In an Active/Passive cluster, you would only have 1 database running on a single node at any given time. Node A is active with 1 DB, Node B is passive with no DBs. Node A goes down, the resources fail over to Node B. Node B is now active with 1 database running on it.
I'm sure more experienced cluster admins or SQL admins will savage me for my terminology, but that's it in a nutshell.
FAQ:
What is the isalive & Looks
alive
LooksAlive check:
LooksAlive is
a basic check in which the Cluster service queries the Windows Service Control
Manager to check if the SQL Server service is still running. By default this
check happens every 5 seconds.
Cluster
service calls looksAlive function every 5 seconds and LookAlive function
Queries the service status by using the Windows NT Service Control Manager.
When the LooksAlive test fails ISAlive test is called immediately.
ISalive Check: A more rigorous IsAlive function is called every 60 second
and monitors the health of the SQL Server by opening up a connection to SQL
Server and issuing “select @@servername” query over the connection. If the
checks fail the online Thread reports this failure to the Cluster Service.
During IsAlive check
the Cluster Service connects to the SQL Server instance with the help of
c:\windows\system32\sqsrvres.dll and runs SELECT @@SERVERNAME against
the instance.
By
default, LooksAlive is fired every 5 seconds and IsAlive is fired every 60
seconds. The LooksAlive and IsAlive polling intervals can be changed in Cluster
Administrator or failover cluster manager from the advanced tab for the SQL
Server resource or using the cluster.execommand prompt utility.
An Active – Passive cluster is
a failover cluster configured in a way that only one cluster node is active at
any given time. The other node, called as Passive node is always online but in
an idle condition, waiting for a failure of the Active Node, upon which the
Passive Node takes over the SQL Server Services and this becomes the Active
Node, the previous Active Node now being a Passive Node.
An Active – Active cluster is a failover cluster
configured in a way that both the cluster nodes are active at any given point
of time. That is, one Instance of SQL Server is running on each of the nodes
always; when one of the nodes has a failure, both the Instances run on the only
one node until the failed node is brought up (after fixing the issue that
caused the node failure). The instance is then failed over back to its
designated node.
Question: List out some of the
requirements to setup a SQL Server failover cluster.
Virtual network name for the
SQL Server, Virtual IP address for SQL Server, IP addresses for the Public
Network and Private Network(also referred as Hearbeat) for each node in the
failover cluster, shared drives for SQL Server Data and Log files, Quorum Disk
and MSDTC Disk.
Question: On a Windows Server 2003
Active – Passive failover cluster, how do you find the node which is active?
Using Cluster Administrator,
connect to the cluster and select the SQL Server cluster. Once you have
selected the SQL Server group, in the right hand side of the console, thecolumn “Owner” gives us the information of the node on which the SQL Server group
is currently active.
Question: How do you open a Cluster
Administrator?
From Start -> Run and type CluAdmin (case insensitive) and the Cluster Administrator console is displayed OR you can also go to Start -> All programs -> Administrative Tools -> Cluster Administrator.
From Start -> Run and type CluAdmin (case insensitive) and the Cluster Administrator console is displayed OR you can also go to Start -> All programs -> Administrative Tools -> Cluster Administrator.
1. How will you
restart your sqlserver on cluster without failing over ..?
Choose
option ( Take offline and Bring online option by right clicking node)
2. What will you if want to add a disk to the SQL Group cluster ..?
Need to choose Add Dependancy option after doing that in Cluster administrator tool (or) in Failover Cluster admin tool from 2008 version
3. As a DBA how will you design active/active cluster requirement . (i.e), how will you manage resource if failed over ..?
Please
read article from MSDN on this to have better understanding
4. Steps for failover ..?
Please
red MSDN on this with full view
5. Difference between SQLSERVER 2005 and SQLSERVER 2008 Cluster Installation ..?
In sql2005 we have the option of installing sql in remaining nodes from the primary node ., But in sql2008 we need to go seperately(Login to the bith nodes) for installing sql cluster .
6. What is the status of services on passive
node for failover cluster in SQL server?
SQL services will be in manual
and stopped. Cluster service will be in automatic and started mode on both the
nodes.
7. Can you move the resources after pausing the node?
Yes resources can be moved after
pausing the node. But we can't move them back till the node is paused.
8.
Where is the prevent failback option?
This is the resource group
property. It doesn't allow the resources to move back to the preferred node
once the node is ready to take the connections after failover.
9.
How does the failover happen? What checks are performed to ensure that
another node is up?
LooksAlive
- The node which host the SQL
server resources is verifed whether this node (server) is up
IsAlive
-
The node which host the SQL server resources is verifed whether the SQL service
is up or not. Basically running SELECT @@SERVERNAME
10.
What will happen if you try to start the fultext service on the passive node.
This
can be started on both the nodes as this doesn't have any dependecy on SQL
service or any resource which is possessed by active node.
11. What is Clustering. Briefly
define & explain it ?
Clustering is a technology, which is
used to provide High Availability for mission critical applications. We can
configure cluster by installing MCS (Microsoft cluster service) component from
Add remove programs, which can only available in Enterprise Edition and Data
center edition.
12. Types of Clusters ?
12. Types of Clusters ?
In Windows we can configure two
types of clusters
1. NLB (network load balancing) cluster for balancing load between
servers. This cluster will not provide any high availability. Usually
preferable at edge servers like web or proxy.
2. Server Cluster: This provides High availability by configuring active-active or active-passive cluster. In 2 node active-passive cluster one node will be active and one node will be stand by. When active server fails the application will FAILOVER to stand by server automatically. When the original server backs we need to FAILBACK the application
2. Server Cluster: This provides High availability by configuring active-active or active-passive cluster. In 2 node active-passive cluster one node will be active and one node will be stand by. When active server fails the application will FAILOVER to stand by server automatically. When the original server backs we need to FAILBACK the application
13. What is Quorum ? A shared storage need to provide for all servers which keeps information about clustered application and session state and is useful in FAILOVER situation. This is very important if Quorum disk fails entire cluster will fails.
14. Why Quorum is necessary ?
When network problems occur, they
can interfere with communication between cluster nodes. A small set of nodes
might be able to communicate together across a functioning part of a network,
but might not be able to communicate with a different set of nodes in another
part of the network. This can cause serious issues. In this “split” situation,
at least one of the sets of nodes must stop running as a cluster.
To prevent the issues that are
caused by a split in the cluster, the cluster software requires that any set of
nodes running as a cluster must use a voting algorithm to determine whether, at
a given time, that set has quorum. Because a given cluster has a specific set
of nodes and a specific quorum configuration, the cluster will know how many
“votes” constitutes a majority (that is, a quorum). If the number drops below
the majority, the cluster stops running. Nodes will still listen for the
presence of other nodes, in case another node appears again on the network, but
the nodes will not begin to function as a cluster until the quorum exists
again.
For example, in a five node cluster
that is using a node majority, consider what happens if nodes 1, 2, and 3 can
communicate with each other but not with nodes 4 and 5. Nodes 1, 2, and 3
constitute a majority, and they continue running as a cluster. Nodes 4 and 5
are a minority and stop running as a cluster, which prevents the problems of a
“split” situation. If node 3 loses communication with other nodes, all nodes
stop running as a cluster. However, all functioning nodes will continue to
listen for communication, so that when the network begins working again, the
cluster can form and begin to run.
15. Different types of Quorum in Windows server 2008 ?
1.Node Majority - Used when Odd
number of nodes are in cluster.
2.Node and Disk Majority - Even
number of nodes(but not a multi-site cluster)
3.Node and File Share Majority -
Even number of nodes, multi-site cluster
4.Node and File Share Majority -
Even number of nodes, no shared storage
16. Different types of Quorum in
Windows server 2003 ?
Standard Quorum : As mentioned above, a quorum is simply a configuration
database for MSCS, and is stored in the quorum log file. A standard quorum uses
a quorum log file that is located on a disk hosted on a shared storage
interconnect that is accessible by all members of the cluster.
Standard quorums are available in Windows NT 4.0 Enterprise Edition, Windows 2000 Advanced Server, Windows 2000 Datacenter Server, Windows Server 2003 Enterprise Edition and Windows Server 2003 Datacenter Edition.
Standard quorums are available in Windows NT 4.0 Enterprise Edition, Windows 2000 Advanced Server, Windows 2000 Datacenter Server, Windows Server 2003 Enterprise Edition and Windows Server 2003 Datacenter Edition.
Majority Node Set Quorums : A majority node set (MNS) quorum is a single quorum
resource from a server cluster perspective. However, the data is actually
stored by default on the system disk of each member of the cluster. The MNS resource
takes care to ensure that the cluster configuration data stored on the MNS is
kept consistent across the different disks.
Majority node set quorums are available in Windows Server 2003 Enterprise Edition, and Windows Server 2003 Datacenter Edition.
Majority node set quorums are available in Windows Server 2003 Enterprise Edition, and Windows Server 2003 Datacenter Edition.
17. Explain about each Quorum type ?
Node Majority: Each node that is
available and in communication can vote. The cluster functions only with a
majority of the votes, that is, more than half.
Node and Disk Majority: Each node
plus a designated disk in the cluster storage (the “disk witness”) can vote,
whenever they are available and in communication. The cluster functions only
with a majority of the votes, that is, more than half.
Node and File Share Majority: Each
node plus a designated file share created by the administrator (the “file share
witness”) can vote, whenever they are available and in communication. The
cluster functions only with a majority of the votes, that is, more than half.
No Majority: Disk Only: The cluster
has quorum if one node is available and in communication with a specific disk
in the cluster storage.
18. How is the quorum information located on the system disk of each node kept in synch?
The server cluster infrastructure
ensures that all changes are replicated and updated on all members in a
cluster.
19. Can this method be used to replicate application data as well?
No, that is not possible in this
version of clustering. Only Quorum information is replicated and maintained in
a synchronized state by the clustering infrastructure.
20. Can I convert a standard cluster to an MNS cluster?
Yes. You can use Cluster
Administrator to create a new Majority Node Set resource and then, on the
cluster properties sheet Quorum tab, change the quorum to that
Majority Node Set resource.
21. What is the difference between a geographically dispersed cluster and an MNS cluster?
A geographic cluster refers to a cluster that has nodes in multiple locations, while an MNS-based cluster refers to the type of quorum resources in use. A geographic cluster can use either a shared disk or MNS quorum resource, while an MNS-based cluster can be located in a single site, or span multiple sites.
21. What is the difference between a geographically dispersed cluster and an MNS cluster?
A geographic cluster refers to a cluster that has nodes in multiple locations, while an MNS-based cluster refers to the type of quorum resources in use. A geographic cluster can use either a shared disk or MNS quorum resource, while an MNS-based cluster can be located in a single site, or span multiple sites.
22. What is the maximum number of nodes in an MNS cluster?
Windows Server 2003 supports 8-node
clusters for both Enterprise Edition and Datacenter Edition.
23. Do I need special hardware to use an MNS cluster?
23. Do I need special hardware to use an MNS cluster?
There is nothing inherent in the MNS
architecture that requires any special hardware, other than what is required
for a standard cluster (for example, there must be on the Microsoft Cluster
HCL). However, some situations that use an MNS cluster may have unique
requirements (such as geographic clusters), where data must be replicated in
real time between sites.
24. Does a cluster aware application need to be rewritten to support MNS?
No, using an MNS quorum requires no
change to the application. However, some cluster aware applications expect a
shared disk (for example SQL Server 2000), so while you do not need shared
disks for the quorum, you do need shared disks for the application.
25. Does MNS get rid of the need for shared disks?
It depends on the application. For
example, clustered SQL Server 2000 requires shared disk for data. Remember, MNS
only removes the need for a shared disk quorum.
26. What does a failover cluster do in Windows Server 2008 ?
26. What does a failover cluster do in Windows Server 2008 ?
A failover cluster is a group of
independent computers that work together to increase the availability of
applications and services. The clustered servers (called nodes) are connected
by physical cables and by software. If one of the cluster nodes fails, another
node begins to provide service (a process known as failover). Users experience
a minimum of disruptions in service.
27. What new functionality does failover clustering provide in Windows Server 2008 ?
New validation feature. With this feature, you can check that your system, storage, and network configuration is suitable for a cluster.
27. What new functionality does failover clustering provide in Windows Server 2008 ?
New validation feature. With this feature, you can check that your system, storage, and network configuration is suitable for a cluster.
Support for GUID partition table
(GPT) disks in cluster storage. GPT disks can have partitions larger than two
terabytes and have built-in redundancy in the way partition information is
stored, unlike master boot record (MBR) disks.
28. What happens to a running Cluster if the quorum disk fails in Windows Server 2003 Cluster ?
In Windows Server 2003, the Quorum
disk resource is required for the Clusterto function. In your example, if the
Quorum disk suddenly became unavailableto the cluster then both nodes would
immediately fail and not be able torestart the clussvc.
In that light, the Quorum disk was a
single point of failure in a MicrosoftCluster implementation. However, it was
usually a fairly quick workaround toget the cluster back up and operational.
There are generally two solutionsto that type of problem.
1. Detemrine why the Quorum disk
failed and repair.
2. Reprovision a new LUN, present it
to the cluster, assign it a driveletter and format. Then start one node with
the /FQ switch and throughcluadmin designate the new disk resource as the
Quorum. Then stop andrestart the clussvc normally and then bring online the
second node.
29. What happens to a running Cluster if the quorum disk fails in Windows Server 2008 Cluster ?
Cluster continue to work but
failover will not happen in case of any other failure in the active node.
30. What
is Failover clusters in sql server
As all of us need every service
should be 24 into 7 and available every time we need that. So every services
provider need to technically strong. TO overcome this problem new concept
comes into picture that is failover cluster. It is group of independent computers
that work together to increase the availability of applications and services.
Here each clustered server connected by cables and by software. And this
clustered server called nodes. If one cluste
|
r nodes fails then another node
begins to work. It is good technique which is not dependent on single server.
|
31. What is the standard setting of Lookslive,
IsAlive and Pending Timeout?
LooksAlive - 5 sec IsAlive - 30 sec Pending Timeout - 180 sec
Note- Do not modify Pending Timeout. The value, represented in seconds, is the amount of time the resource in either the Offline Pending or Online Pending states has to resolve its status before the Cluster Service puts the resource in either Offline or Failed status.
32. Can you change failover policy? If Yes then how?
To configure the failover policy, in the Threshold box, enter the number of times the group is allowed to fail over within a set span of hours. In the Period box, enter the set span of hours. For example, if Threshold is set to 10 and Period is set to 6, the Cluster Service fails the group over a maximum of 10 times in a 6-hour period. At the 11th failover in that 6-hour period, the server cluster leaves the group offline. This affects only resources that were failed over; therefore, if the SQL Server resource failed 11 times, it would be left offline, but the IP could be left online.
33. What is the status of the Cluster Service and SQL service on both the nodes? Would they both were stop on the passive node?
Cluster service is automatic and started mode on all the nodes.
But SQL Service will run only on the active node.
34. Is it possible to put Cluster Group and SQL Group on different nodes?
Yes it is Possible. If you have one group on one node and
another group on another node... that will run.
35. Do you know any kind of limitation for Clustering?
35. Do you know any kind of limitation for Clustering?
Yes, We cannot do clustering with Windows 2000 Professional or
lower server versions. Clustering is only available on servers running Windows
2000 Advanced Server (which supports 2-node clusters), Windows 2000 Datacenter
Server (which supports up to 4-node clusters), or Windows 2003 Enterprise
Edition and Windows 2003 Datacenter Server (which support up to 8-node
clusters).
36. How does Cluster perform at the time of failover?
36. How does Cluster perform at the time of failover?
Clusters use an algorithm to detect a failure, and use failover
policies to determine how to handle the work from a failed server. These
policies also specify how a server is to be restored to the cluster when it becomes
available again.
37. What are all resources controlled by Cluster?
The short list of resources controlled by the cluster will be-
•Physical Disks (Q:—Quorum disk, E:—Shared disks, F:, so on)
•Cluster IP Address
•Cluster Name (Network Name)
•MS DTC
•SQL Server Virtual IP Address
•SQL Server Virtual Name (Network Name)
•SQL Server
•SQL Agent
•SQL Full Text Service Instance (if installed)
38. How to configure MSDTC as a cluster resource?
Setup DTC using following command
C:\Windows\System32> DTCSetup.exe
“OR”
From a DOS command prompt, run comclust.exe on node A. This will configure MS DTC for use with cluster services.
C:\Windows\System32> comclust.exe
39. Whatis isalive and look alive?
Is Alive check: An exhaustive check to verify that a resource is running properly. If this check fails, the resource is moved offline and the failover process is triggered. During the Is alive check the cluster service connects to the SQL server instance and execute select @@SERVERNAME.It will check only the SQL server instance availability and does not check the availability of user databases.
•Physical Disks (Q:—Quorum disk, E:—Shared disks, F:, so on)
•Cluster IP Address
•Cluster Name (Network Name)
•MS DTC
•SQL Server Virtual IP Address
•SQL Server Virtual Name (Network Name)
•SQL Server
•SQL Agent
•SQL Full Text Service Instance (if installed)
38. How to configure MSDTC as a cluster resource?
Setup DTC using following command
C:\Windows\System32> DTCSetup.exe
“OR”
From a DOS command prompt, run comclust.exe on node A. This will configure MS DTC for use with cluster services.
C:\Windows\System32> comclust.exe
39. Whatis isalive and look alive?
A:
Looks Alive check:Looks alive
check is a basic resource health check to verify that the service(SQL service
in our context) is running properly.To perform this , cluster service queries
the windows service control manager to check the status of the service.By
default looks alive check will happen in every five seconds.
Is Alive check: An exhaustive check to verify that a resource is running properly. If this check fails, the resource is moved offline and the failover process is triggered. During the Is alive check the cluster service connects to the SQL server instance and execute select @@SERVERNAME.It will check only the SQL server instance availability and does not check the availability of user databases.
You
can specify two polling intervals and a timeout value for resources. The
polling intervals affect how often the MSCS Resource Monitor checks that the
resource is available and operating. There are two levels of polling; they are
known in Cluster Administrator as "Looks
Alive" and "Is
Alive." These values are named for the calls that
the Resource Monitor makes to the resource to perform the polling. In
"Looks Alive" polling, MSCS performs a cursory check to determine if
the resource is available and running. In "Is Alive" polling, MSCS
performs a more thorough check to determine if the resource is fully
operational. The timeout value specifies how many seconds MSCS waits before it
considers the resource failed.
40. What is Quorum?
A:
Quorum is the cluster's configuration file.This file
(quorum.log) resides in the the quorum disk (one disk from shared disk
array).Quorum is the main interpreter between all nodes. It stores latest
cluster configuration and resource data. This helps the other nodes to take
ownership when one node goes down.
No comments:
Post a Comment