The Battery-Backup Cache can be installed on IBM ServeRAID II and 3H Adapters. The Battery-Backup Cache does not disable the cache memory SIMM already attached to the IBM ServeRAID II Adapter, nor is the memory capacity increased by its installation.
The Battery-Backup Cache mirrors only the dirty data in the SIMM. Dirty data is data that is stored in the memory SIMM that has not been written to the hard drives. In write-back mode the ServeRAID II Adapter notifies the host that it has completed the write operation even though the data hasn't yet been written to the hard drive.
An adapter with 32 MB of cache memory can use either an 8 MB or a 32 MB Battery-Backup Cache. However, a 32 MB Battery-Backup Cache will provide better performance.
While write-back mode improves performance, dirty data is in jeopardy of being lost in the event of a system malfunction or power loss.
If a ServeRAID adapter/controller equipped with a Battery-Backup Cache fails, it can be removed and installed on a working adapter. The data on that Battery-Backup Cache can then be flushed into the memory SIMM located on the new adapter and written to the disk.