HP MSA Controllers - Manual (Page 21)

HP P2000 G3 FC/iSCSI MSA System User Guide 21
NOTE: See HP P2000 G3 MSA System SMU Reference Guide for more information about volume cache
options.
Transportable CompactFlash
During a power loss or array controller failure, data stored in cache are saved off to non-volatile memory
(CompactFlash). These data are then written to disk after the issue is corrected. To protect against writing
incomplete data to disk, the image stored on the CompactFlash is verified before committing to disk.
In single-controller configurations, if the controller has failed or does not start, and the Cache Status LED is
on or blinking, the CompactFlash will need to be transported to a replacement controller to recover data
not flushed to disk (See Controller failure in a single-controller configuration on page 55 for more
information).
CAUTION: To preserve the existing data stored in the CompactFlash, you must transport the
CompactFlash from the failed controller to the replacement controller using a procedure outlined in the HP
Controller Module Replacement Instructions, shipped with the replacement controller. Failure to use this
procedure will result in the loss of data stored in the cache module. The CompactFlash must stay with the
same enclosure. If the CompactFlash is used/installed in a different enclosure, data loss/data corruption
will occur.
IMPORTANT: In dual controller configurations featuring one healthy peer controller, there is no need to
transport a failed controller’s cache to a replacement controller because the cache is duplicated between
the controllers.
Super-capacitor pack
To protect RAID controller cache in case of power failure, P2000 G3 MSA System controllers are equipped
with super-capacitor technology, in conjunction with CompactFlash memory, built into each controller
module to provide unlimited cache memory backup time. The super-capacitor pack provides energy for
backing up unwritten data in the write cache to the CompactFlash in the event of a power failure. Unwritten
data in CompactFlash memory are automatically committed to disk media when power is restored. While
the cache is being maintained by the super-capacitor, the Cache Status LED flashes at a rate of 1/10
second on and 9/10 second off.
Controller Module
CompactFla s h