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Re: [linux-lvm] cLVM commands often taking a long time to execute

Thank you, Vladislav, for the suggestion.  That could potentially help in cases where the nodes are CPU-bound, likely independent of whether they are I/O-bound.


Robert Riches

-----Original Message-----
From: linux-lvm-bounces redhat com [mailto:linux-lvm-bounces redhat com] On Behalf Of Vladislav Bogdanov
Sent: Thursday, November 10, 2011 1:06 AM
To: linux-lvm redhat com
Subject: Re: [linux-lvm] cLVM commands often taking a long time to execute

09.11.2011 03:06, Riches Jr, Robert M wrote:
> I'm running into some odd behavior from clustered LVM commands on a 
> 3-node pacemaker-based cluster.  When other processes on the nodes are 
> doing somewhat heavy sequential I/O traffic, LVM commands such as lvs, 
> pvs, vgs, lvdisplay, pvdisplay, and vgdisplay have widely variable, 
> often very long execution times.  The same LVM command done 
> repetitively will have execution times varying from less than a second 
> to 10-15 seconds, more rarely up to around 60 seconds.  Other 
> read-heavy commands such as find, wc, and sum have much less 
> variability and much shorter tails in the distribution of their execution times.
> Is it known what causes the cLVM commands to be so slow at times?
> Perchance, are there known ways to get cLVM commands to be less slow?

I use chrt -r 99 for them. And I also run clvmd the same way. But this is much more about CPU load then IO load.
Also, please make sure that you correctly filter unneeded block devices from being PV-suspects (filter clause in lvm.conf).


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