Application clusters

An application cluster is characterized by:

• 2 servers with the same operating system: Windows, Linux, AIX or Solaris
• The same application installed on both servers
• SafeKit installed on both servers
• An application module installed on both servers

An application module is a pre-configured SafeKit high-availability solution for one application. Two types of clustering architecture are available for an application module:

• A farm cluster provides network load balancing and automatic failover
• A mirror cluster provides real-time file replication and automatic failover.

We talk in terms of mono-module when a single application module is implemented on a physical cluster, and multi-module when several application modules are implemented on the same physical cluster. The multi-module approach allows you to implement interesting architectures, such as mixed farm and mirror on the same cluster, active/active with 2 servers in mutual takeover, and n-to-1 with n active servers and a single backup.

Multi-module example

The diagram shows a multi-module configuration with 5 application modules on a cluster of 2 physical servers:

• An apache_farm.safe application module: active/active with network load balancing and failover for the Apache web service
• An iis_farm.safe application module: active/active with network load balancing and failover for the IIS web service
• An oracle.safe application module: active/passive with real time file replication and failover for Oracle databases
• A sqlserver.safe application module: active/passive with real time file replication and failover for Microsoft SQL Server databases
• A mysql.safe application module: active/passive with real time file replication and failover for MySQL databases

Want to know more?

• Click here for the full list of modules delivered with SafeKit
• Click here to understand an alternative technique: virtual server clustering
• Click here to learn how to choose between virtual server clustering and application clustering