The application must be capable of storing all required data and configuration information on shared disks. The exception to this rule is a true shared nothing cluster.

To meet this requirement, you may need specific setup options or soft links. For example, a product may only install in /usr/local. This limitation requires one of the following options: linking /usr/local to a file system that is mounted from the shared storage device or mounting file system from the shared device on /usr/local.

The application must also store data to disk instead of maintaining it in memory. The takeover system must be capable of accessing all required information. This requirement precludes the use of anything inside a single system inaccessible by the peer. NVRAM accelerator boards and other disk caching mechanisms for performance are acceptable, but must be done on the external array and not on the local host.