This integer reports the amount of memory, in kilobytes, allocated for read caching, noting the usable amount is halved due to mirroring, and that read cache always returns 0 on older IDA, IDA-2, and SMART controllers which don't support it. An admin uses this to confirm how much read-ahead cache capacity a given controller actually provides. For example, cpqDaAccelReadMemory reporting 0 on a controller model that predates read caching support tells the admin not to expect read-cache benefits from that hardware.