A messaging engine in a cluster bus member can fail over
between servers in the cluster, but the messaging engine must be able
to access the saved state in its file store from any
of the cluster servers.
File stores can be used in highly available environments. In order
to make a file store highly available, use hardware or software facilities
that can maximize the availability of the file store data, for example,
a storage area network (SAN).
Note: You must ensure that the directories
containing the log file and store files can be accessed from all members
of the cluster, by using the same directory name.
WebSphere® Application Server supports
two styles of file system access to enable high availability:
- Cluster-managed file system
- This style of file system access uses high availability clustering
and failover of shared disks to ensure that the directories for the
file store are accessible from the server that is currently running
the messaging engine. The directories are located on file systems
in the shared disks, and high availability cluster scripts are used
to mount the file systems on the node that contains the server that
is running the messaging engine.
- Networked file system
- This style of file system access allows remote files to be accessed
over a network. The most popular protocols for accessing remote files
are Common Internet File System (CIFS) and Network File System (NFS).
Version 4 of NFS supports automated failover to ensure access locking.
Access locking ensures the integrity of the log files; that is, only
a single client process can access the log at a time.
Note: It is important to check that the file system configuration
is correct, because it cannot be checked by the WebSphere Application Server configuration system
or messaging engine. Errors only surface at run time, so thorough
failover testing is recommended.