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From: Matthew Gillen <me@mattgillen.net>
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Subject: Re: [linux-lvm] LVM2 resync speed problems
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To: LVM general discussion and development <linux-lvm@redhat.com>

Leonard Smith wrote:
> I am running CentOS4.4 on  two "black" box systems that are
> identically configured. Both have 500 GB internal drives, ( same type)
> and were installed using the same kickstart configuration. The drives
> are being mirrored using LVM.
> 
> When I check the first system it is re-syncing and the resync time and
> speed are
> 
> finish=18559.6min speed=355K/sec
> 
> On the second system the time and speed are
> 
> finish=89.5min speed=68170K/sec
> 
> I can't figure out why the speeds are different between the two. I
> checked /proc/sys/dev/raid/speed_limit_ and they are the same. The
> priority of the md proceses are they same.
> 
> I tweaked the setting of the speel_limit_min and increase the nice
> priority of the resync process, on the first box, but I could never
> get it better than
> 
> finish=4551.8min speed=1445K/sec
> 
> 
> I've googled and I haven't found much more useful information that to
> adjust those settings. Besides those setting what else dictates the
> speed used?

You might compare the hd settings using 'hdparm'.  I'm not sure factor of 100+
can be explained by an incorrect DMA setting or something like that, but it
might be a contributor.

Matt