2.2.4 What are Server Pools?

A server pool is a required entity in Oracle VM, even if it contains a single Oracle VM Server. In practice, several Oracle VM Servers will form a server pool, and an Oracle VM environment may contain one or several server pools. Server pools are typically clustered, although an unclustered server pool is also possible.

Server pools have shared access to storage repositories and exchange and store vital cluster information in the server pool file system. In a server pool, a Master server is elected, which is responsible for centralized communication with the Oracle VM Manager. If necessary, any other member of the server pool can take over the Master role. Even in case of server failure, the server pool remains accessible at its virtual IP address, which all servers in the pool share. Since server pools have shared access to storage repositories, live migration of virtual machines is possible for load balancing or for scheduled maintenance, so that a virtual machine can be moved from one Oracle VM Server to another without an interruption of service.

Within a clustered server pool, virtual machines have high availability or HA. The clustering technology used within Oracle VM can take care of monitoring the status of all of the Oracle VM Servers belonging to the server pool. If a pool member disappears for whatever reason, its virtual machines can be recovered and brought back up on another Oracle VM Server because all necessary resources are available on shared storage.

A detailed explanation of the purpose of a server pool and the technology used within one is provided in Chapter 6, Understanding Server Pools and Oracle VM Servers.