Cache Memory
Cache Memory holds the write-cache modules that plug onto RAID controllers. HP Smart Array battery-backed (BBWC) and flash-backed (FBWC) modules cover the P212, P410, P411, P400, P400i, E200i, 641, 642 and 5300 series, with P-Series and B-Series FBWC kits from 512MB to 1GB. There's Dell PERC 5/i cache for the PowerEdge 1950 and 2950 and a 4GB cache module for HP StorageWorks XP arrays. Without a working cache module, or with a failed battery or capacitor, these controllers turn off write caching and writes slow down noticeably.
Cache Memory: 66 products
Buying guide
Replacing controller cache
Controller family
Cache modules are keyed to a controller generation. FBWC for the P410 and FBWC for the Gen8 P420 look alike but aren't interchangeable.
Battery or capacitor pack
Each module depends on a battery or capacitor pack and its cable. Replace a worn pack along with the module, or write caching stays off.
RAID levels
On some Smart Array controllers, RAID 5 and RAID 6 are available only with a cache module installed.
Cache Memory
Frequently asked questions
What happens to cached data if the power fails?
With BBWC, the battery keeps the cache contents alive for a limited time, and the data is written to disk when power returns. FBWC copies the cache to flash, so the data waits safely until the server restarts.
How do I know if my cache battery has failed?
The server's management tools, such as HP Smart Storage Administrator, iLO or the POST messages at boot, report the battery or capacitor status and show when write caching has been disabled.
Does a cache module add memory to the server?
No. It sits on the RAID controller and only buffers disk reads and writes. System memory is separate and goes in the motherboard's DIMM slots.
