I have a few questions about RAID 5, BBWC (Battery Backed Write Cache), filesystem (ext3) and optionally mysql.
I have a hypothesis and I ask Server Fault community to validate or not this one:
-The system is UP, applications works with database and use transactions
-The RAID system is configured with RAID5,write caching and battery (BBWC)
With this solution, when OS receive write ACK, data are possibly in the RAID controller cache, and not in a persistent memory (my RAID drives disk).
If a power failure appears and data are in the RAID controller cache, the BBWC maintains data with the battery pack. Until then, everything is good.
But battery has a certain capacity, and it’s not infinite. If the power failure is longer than two or three days, the RAID cache is lost.
For me it’s a dramatic and likely scenario.
My questions are:
Ext3 can solve this problem? Probably not
Is it possible to corrupt mysql database?
Mysql transactions are lost? I think so
Thank you for your help
Hardware: HP DL380 G7
OS: Centos 5 with ext3