Re: 1 week to rebuid 4x 3TB raid10 is a long time!

[Bob Marley <bobmarley@shiftmail.org>]

On 20/07/2014 10:45, TM wrote:
> Hi,
>
> I have a raid10 with 4x 3TB disks on a microserver
> http://n40l.wikia.com/wiki/Base_Hardware_N54L , 8Gb RAM
>
> Recently one disk started to fail (smart errors), so I replaced it
> Mounted as degraded, added new disk, removed old
> Started yesterday
> I am monitoring /var/log/messages and it seems it will take a long time
> Started at about 8010631739392
> And 20 hours later I am at 6910631739392
> btrfs: relocating block group 6910631739392 flags 65
>
> At this rate it will take a week to complete the raid rebuild!!!
>
> Furthermore it seems that the operation is getting slower and slower
> When the rebuild started I had a new message every half a minute, now it’s
> getting to OneAndHalf minutes
> Most files are small files like flac/jpeg
>

Hi TM, are you doing other significant filesystem activity during this 
rebuild, especially random accesses?
This can reduce performances a lot on HDDs.
E.g. if you were doing strenous multithreaded random writes in the 
meanwhile, I could expect even less than 5MB/sec overall...