Understanding the concept
A failover cluster is a group of independent computers that work together to increase the availability of applications and services. The clustered servers (called as nodes) are connected by physical cables and by software. If one of the cluster nodes fails, another node begins to provide service so that users experience a minimum of disruptions in service. In an organization they put a lot of value on mission-critical servers and rely on them heavily to run their businesses. As a result, server downtime can be very costly. For example, Unexpected down time of a heavily used e-mail, database server or any other service can easily lost productivity or lost business for every hour that it is unavailable. In this case clustering can be used as a way to achieve high availability of these services.
Before configuring windows clustering we must make sure that you meets the below requirement,
1. The failover cluster feature is not available in Windows Web Server 2008 or Windows Server 2008 Standard.
2. It is recommended to have a dedicated network interface for failover clustering. So in a clustered server it is will have its existing NIC and an additional one that we are adding for now. Its not necessary to have additional NIC card but MS highly recommend this.
3. Since we are adding additional NIC card it is necessary to assign IP address to those and make sure that these addresses are static(Do not assign IP address through DHCP).
4. It is necessary to assign an IP address for clustering as well. So make sure that you have an IP address which can be assigned to it. Please note that if you have different networks in your server, we need to assign each network with its own IP address.
5. Make sure that each servers which are going to take part in clustering is same edition. Means either all the servers should be either Enterprise or Datacenter edition.
6. The user which are going to perform this action should have proper privilege on active directory(Delegated control to add and remove computers and users in AD) or administrative privilege.
Refer the below link for more information http://technet.microsoft.com/en-us/library/cc771404.aspx .
Installation and Configuring Windows failover clustering
We must make sure that you have added the relevant storage disks to server. If you are mapping the storage through iSCSI, you must map it using iSCSI initiator. Once the disks are attached through it, open disk management and newly added disks will be listed. These disks will be in the state of offline. Right click on the disk and select Online and convert those disk into New spanned volume. Performing this steps will allow you to list the storages are available for cluster. You need to do the same on all the servers which are going to take part in clustering. Those steps are required only if you are adding the storage disk to failover clustering now and note necessary for cluster basic configuration.
1. Now make sure that the feature Failover clustering and multipath I/O is installed on all the nodes that are going to be the part of failover clustering.
Open Server manager->Features->Add feature. Now on the window Select features tick the check boxes for Failover clustering and multipath I/O, click Next.
2. Click on the button Install and wait for this to complete. Once it is succeeded close the windows.
3. I would recommend you to reboot the servers which are installed with these features.
4. Please note that here I am configuring two servers as part of failover clustering(Server-1 and Server-2). There are 3 storage disk attached to my both the servers using iSCSI initiator.
Once the servers are up, Open Failover cluster manager from Administrative tools. Before the cluster configuration, we can check whether the current configurations on the servers(Which are going to be the part of cluster) are suitable for failover clustering. It is highly recommended to perform this test so that we can avoid the failures during the configuration or the issues that may arise after configuration. Validating cluster configuration wizard performs the tests in mainly 4 areas that are,
a) Inventory b) Network c)Storage d) System configuration
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 your 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 system software and configuration settings are compatible across servers.
Refer the this link for more details http://technet.microsoft.com/en-in/library/cc772055.aspx .
In order to perform the test, Right click on Failover cluster manager and select Validate a configuration wizard. Click Next on before you begin window which is explained about the tests that we are going to do now.
5. Now you need to specify the servers which are going to be the part of clustering. Type the host name or IP address of each servers and press ENTER. Once the servers are added click Next to continue.
6. Here we have to select which and all the tests that we need to perform now. These tests are as described in step 4 and its sub parts. If this is the first time that you are running the test I would recommend to select Run all test, and click Next. Where as you can select and run only the test that are required, this is mainly used when you find any error after the initial test and you need to check whether the corrections that you made has made any changes.
7. Click Next on confirm window and it will start the test.
8. Once the tests are completed you will have the below window and you must review the test results. If the test results reports any errors you will not be able to configure the cluster and you must resolve those issues. You may have suggestions as well to resolve the issue. The test results will also contain warning messages as well, review the messages and try to resolve as much.
9. Assuming everything is well for you as well. Now you can start the cluster configuration, right click on Failover cluster manager and select create cluster wizard. Click Next on Before you begin.
10. Add the servers which are all going to be the part of clustering. Enter the host name or IP address of the server and press ENTER else you can browse the servers, Click Next.
11. Now you need to specify the cluster name that you would like to. You can specify the name as your wish and note that the NetBIOS name is limited to 15 characters and if it exceeds it will automatically reduce and get first 15 characters of specified name also there should not be any spaces in cluster name. Also as described in the requirements of clustering we should specify a IP address which will be referred as cluster IP. If you have more than one networks defined in your server, you must specify different cluster IP for each network.
Click on Network address and type the IP address, make sure that the IP is not provided by DHCP and it should be static, Click Next.
12. Click Next on confirmation window to start the cluster configuration and wait for some time to complete this operation.
13. Once the cluster is configured you will have the below window which indicates that the cluster configuration is successfully completed. You can review the reports or click Finish to close the window.
14. Performing the above steps will complete the cluster configuration which defines which are all the servers are going to act as failover servers. I hope the step 1 has helped you to add the shared disk to your server(Using iSCSI). Now those disks are to be added to cluster so that it can act as failover.
Expand the newly created cluster and right click on the folder structure Storage. Select Add storage and If the disk are configured properly as cluster storage then those will list out automatically without any other change. Here I have 3 disks created so it will list and I am selecting all those as the part of clustering, click OK.
Now you can see the disks that are available and they are part of cluster.
15. Now we need to configure quorum of the cluster. Quorum configuration of a cluster defines the number of failure that the cluster can sustain. It is essential that the cluster stop running if too many failures occur or if there is a problem with communication between the cluster nodes. Quorum can be defined in four way depending on your configurations. We will discuss about it in below steps.
To start with quorum configuration right click on the cluster that you have created now->More actions->Configure cluster quorum settings. Click Next on before you begin window.
16. As described above here we need to specify which quorum configuration is required for you and its based on your nodes that are defined as part of failover clustering. I hoe you are clear with why do we need quorum in clustering. Now let us see its configuration types. There are four ways to achieve this,
Node Majority - This configurations are recommended only when you have odd number of nodes(servers) . That is, when you have configured your failover clustering with odd number of servers you must go for this option. The number of failures that can sustain for clusters under this configuration is half the number of nodes minus one. For example, If you have seven servers in cluster it can have maximum of three node failures.
Node and Disk Majority- It is recommended when you have an even number of nodes(servers). The number of failures that this cluster can opt is based on disk witness.
If the disk witness remains online it can sustain failures of half the nodes. For example, an eight node cluster in which the disk witness is online could sustain four(8/2=4) node failures.
If the disk witness goes offline the cluster can sustain failures of half the nodes minus one. For example, a six node cluster with a failed disk witness could sustain two (3-1=2) node failures.
Node and File Share Majority- It works in a similar way to Node and Disk Majority, but instead of a disk witness, this cluster uses a file share witness. Note that if you use Node and File Share Majority, at least one of the available cluster nodes must contain a current copy of the cluster configuration before you can start the cluster. Otherwise, you must force the starting of the cluster through a particular node.
No Majority: Disk Only- This is the least considered configuration and not recommended. It can sustain failures of all nodes except one (if the disk is online). However, this configuration is not recommended because the disk might be a single point of failure.
In my case I have two nodes so I will select the second option and click Next. You must decide the selection based on your cluster configuration.
17. Now you need to specify the storage which will contains a copy of the cluster configuration, called as disk witness. Select the node which is required to act as your witness disk and click Next(Here the disk will be listed that are added to our cluster storage as per step 14). Note that if you have select Node and File Share Majority you need to specify the shared location.
18. Now you will have the window to confirm the actions. Review the details and click Next.
19. The quorum configuration will start and you will have the below windows. Once it is completed you can review the details and click Finish to close window.
So that completes the Windows failover clustering installation and configuration. You can confirm whether the clustering has completed successfully by taking one node as offline(Shutdown/restart) or right click the active node and from more actions Stop cluster service and on another node login and check if the disks are available.