A server cluster (MSCS) is a collection of servers that together provide a single, highly available platform for hosting applications. Applications can be failed over to ensure high availability in the event of planned downtime due to maintenance or unplanned downtime due to hardware, A Server cluster can consist of up to eight nodes. Each node is attached to one or more cluster storage devices. Cluster storage devices allow different servers to share the same data, and by reading this data provide failover for resources. Operating System or application failures. Server clusters provide a highly available platform for applications such as SQL Server, Exchange Server data stores, file and print servers, etc. Server clusters are used for stateful applications that rely on some state context from one request to the next.
Server cluster and Failover
When a node is active, it makes its resources available. Clients access these resources through dedicated virtual servers. Server cluster uses the concept of virtual servers to specify groups of resources that failover together. When a server fails, the group of resources configured on that server for clustering fails over to another server. The server that handles the failover should be configured for the extra capacity needed to handle the additional workload. When the failed server comes back online, Server cluster can be configured to allow failback to the original server, or to allow the current server to continue to process requests.
Cluster Storage Devices
Cluster storage devices should be optimized based on performance and availability needs.A redundant Array of Independent Disks (RAID) 5 configuration for clusters is recommended.
Private and Public Network Addresses
Typically nodes in a cluster are configured with both private and public network addresses.
- Private network addresses are used for node-to-node communications.
- Public network addresses are used for client-to-cluster communications.
Some clusters may not need public network addresses and instead may be configured to use two private networks. In this case, the first private network is for node-to-node communications and the second private network is for communicating with other servers that are a part of the service offering.