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List:       linux-raid
Subject:    Re: raid5 grow reshaping speed is unchangeable
From:       Richard Scobie <richard () sauce ! co ! nz>
Date:       2007-12-29 4:38:12
Message-ID: 4775CF34.7030400 () sauce ! co ! nz
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Cody Yellan wrote:

> You are right, Richard.  RHEL5 had a stripe_cache_size of 256 when
> the reshape began.  I increased it to 1024 and the reshape speed
> doubled to 4500K/s.  I did not see any increase in memory usage.  I
> tried 2048 and then 4096 but saw no difference in speed.

Sorry, I did not make myself clear.

Back when I was seeing the slow resync speeds, it was due to larger than 
default stripe_cache_size - I had increased to 16384.

When this was reduced back to the default, which I suspect is 256, 
speeds were back up to more normal levels - much faster than the 4.5MB/s 
you are seeing.

At some point, this issue was fixed and currently on 2.6.22, with a 
stripe_cache_size of 16384 and a 4 x 500GB SATA II md RAID 5, resync 
speed is 162MB/s.

Perhaps somthing different occurs on a reshape, (which I have only now 
realised you were doing).

Regards,

Richard
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