Areca 24/4 Internal/External Port Pcie 3.0 12 Gb/s SAS/SATA Raid Controller 2Gb Cache - Manual (Page 254)

APPENDIX
254
Data Protection
• Battery Backup
The RAID controllers are armed with a Battery Backup Mod-
ule (BBM). While a Uninterruptible Power Supply (UPS) pro-
tects most servers from power fluctuations or failures, a BBM
provides an additional level of protection. In the event of a
power failure, a BBM supplies power to retain data in the RAID
controller’s 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. Un-
der 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
executed by the I/O processor. The firmware can also be up
dated through the RAID controllers PCIe bus 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
firmware. With our Redundant Flash Image feature, the con-
troller will revert back to the last known version of firmware
and continue operating. This reduces the risk of system failure
due to firmware crash.