Saturday, June 20, 2009

Two-Node Failover Cluster in Windows Server 2008 r2

In this blog entry I decided to create a demo to help you to get starting with Microsoft Cluster Services. I'm not going into much detail on every aspect of clustering but you should be aware that clustering has some special requirements for apps and hardware, make sure you follow them before starting to build or think to create one.

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, the other node begins to provide the service that fail in the first one (this process is known as failover). By doing this the users experience a minimum of disruptions in service and the business doesn't stop because of the failed node.

Clusters are used to provide high availability to mission-critical applications. Failover clustering can help you build redundancy into your network and eliminate single points of failure for apps, services that are critical to your business. In the network infrastructure that connects your cluster nodes, avoid having single points of failure. You can connect your cluster nodes by multiple, distinct networks. Alternatively, you can connect your cluster nodes with one network that is constructed with teamed network adapters, redundant switches, redundant routers, or similar hardware that removes single points of failure.

Cool!!! Well... yes it's nice to have a group of servers to provide availability but nothing comes for free, and clusters can be expensive.

In today’s world there're many apps that are mission-critical for business needs, and without those apps running your company may lose lots of money because of that. Mail Servers, Database Servers, Virtualization Servers, Print Servers are just few examples in many other possible scenarios where clusters are used.

Two Node Cluster:
- Before starting, check Failover Cluster Requirements here.

- In this demo we'll use 2 servers with identical hardware and OS (Windows 2008 r2) and the same SP level.

- Both nodes are part of Active Directory Domain as member servers.

- The account that I'll use to configure the Cluster does not need to be a Domain Admins account, but needs to be a Domain Users account that is in the Administrators group on each clustered server (or the group that the account is a member of). In addition, if the account is not a Domain Admins account, the account (or the group that the account is a member of) must be given the Create Computer Objects permission in the domain. If your Domain Admin don't want to give you that privilege you must request or pre-create the Computer Object in a Disabled state. After creating the Computer Account you must give 'Full Control' permission to the user (or to the group that the account is a member of) for that Computer account prior to creating the cluster.

- The cluster should have in both nodes 2 NICs, one for Public communications (the clients use this interface to communicate with the cluster), and other for Private communications (only between both nodes "Heartbeat").

- For this two-node cluster, the quorum configuration will be Node and Disk Majority. Node and Disk Majority means that the nodes and the witness disk each contain copies of the cluster configuration, and the cluster has quorum as long as a majority (two out of three) of these copies are available that provides the specific permissions and privileges that are necessary for the service (similar to the local system context, but with reduced privileges).

- Remember that you must use shared storage that is compatible with Windows Server 2008. If you are using Serial Attached SCSI or Fiber Channel, in all clustered servers, the mass-storage device controllers that are dedicated to the cluster storage should be identical. They should also use the same firmware version (With Windows Server 2008, you cannot use parallel SCSI to connect the storage to the clustered servers.).

Heve Fun :)

No comments:

Post a Comment