2007/10/27, Rui Santos <rsantos(a)ruisantos.com>om>:
Try to think of a RAID Array as a single partition. You put a filesystem
"on top" of a partition or a RAID Array.
I know it's logically a partition/disk, but the important bit there is
"logically", a real partition won't melt down or break into multiple
If the power fails, the -partition- DOES
"survive". The filesystem may
have inconsistencies but it is probably recoverable.
It is the same principle ( almost ) with a Soft-RAID array.
If you have frequent power loss, IMHO, you should activate RAID
write-intent bitmapping. The command is mdadm /dev/mdX -Gb internal
That's what i'm talking about, i wonder if that has a performance
penalty. This is the result of the last power outage:
mainwks:~ # cat /proc/mdstat
Personalities : [raid1] [raid0] [raid6] [raid5] [raid4] [linear]
md0 : active raid1 sda1 sdb1
104320 blocks [2/2] [UU]
md1 : active raid1 sda3 sdb3
241987008 blocks [2/2] [UU]
[==>..................] resync = 11.0% (26760192/241987008)
I assume that would look really nasty on a big raid5...
If you are afraid about a RAID's inconsistency by issuing "echo check >>
and check for failures wiht "cat /sys/block/mdX/md/mismatch_cnt".
If there are failures, correct it with "echo repair >>
You can also put it on a cron script...
Hope it helps,
I will look further on the bitmapping topic.
Thanks a lot
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