APPENDIX
104
cache, thereby permitting any potentially dirty data in the cache
to be flushed out to secondary storage when power is restored.
The batteries in the BBM are recharged continuously through
a trickle-charging process whenever the system power is on.
The batteries protect data in a failed server for up to three or
four days, depending on the size of the memory module. Under
normal operating conditions, the batteries last for three years
before replacement is necessary.
• Recovery ROM
RAID controller firmware is stored on the flash ROM and is ex-
ecuted by the I/O processor. The firmware can also be updated
through the RAID controllers Thunderbolt port or Ethernet port
without the need to replace any hardware chips. During the
controller firmware upgrade flash process, it is possible for a
problem to occur resulting in corruption of the controller firm-
ware. With our Redundant Flash Image feature, the controller
will revert back to the last known version of firmware and con-
tinue operating. This reduces the risk of system failure due to
firmware crash.
