Re: Howto avoid full re-sync

Am 07.09.2012 um 06:41 schrieb Adam Goryachev:

I have a MD raid6 with 5 drives, and every now and then one (random)
drive will fail. I've done all sorts of checks, and the drive is
actually working fine, so I suspect an issue with the Linux driver
and/or SATA controller (onboard).

It isn't really relevant to the question, but I'll run through the sata
stuff, in case anyone can point out a simple solution to stop this from
happening (yes, a new server is on the way, but with budgets etc, that
could be some time away. This issue has happened for years, but we are
becoming more active with these failures now).

00:0e.0 IDE interface: nVidia Corporation MCP51 Serial ATA Controller
(rev a1)
00:0f.0 IDE interface: nVidia Corporation MCP51 Serial ATA Controller
(rev a1)
01:07.0 RAID bus controller: Silicon Image, Inc. Adaptec AAR-1210SA SATA
HostRAID Controller (rev 02)

cat /proc/mdstat
Personalities : [raid1] [raid6] [raid5] [raid4]
md2 : active raid6 sdh1[5] sdg1[4] sdf1[0] sdd1[6](F) sde1[2] sda1[1]
     5860535808 blocks level 6, 64k chunk, algorithm 2 [5/4] [UUU_U]
     [>....................]  recovery =  1.4% (28663240/1953511936)
finish=486.5min speed=65938K/sec



Since I know sdh is actually almost up to date, is there some way to
re-add it, and only have to sync the portions of the disk which have
changed?

Besides all the stuff about fix your server, a raid is not a backup and you risk your data - simply add a write intent bitmap:

# mdadm /dev/md2 --grow bitmap=internal

Best regards
Ralf