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

[Vladislav Bogdanov]

10.11.2011 19:16, Riches Jr, Robert M wrote:
> 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.

Except filtering unneeded block devices. This greatly helps in IO-bound
setups.

> 
> Thanks,
> 
> Robert Riches
> 
> -----Original Message----- From: linux-lvm-bounces at redhat.com
> [mailto:linux-lvm-bounces at redhat.com] On Behalf Of Vladislav
> Bogdanov Sent: Thursday, November 10, 2011 1:06 AM To:
> linux-lvm at 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).
> 
> Best, Vladislav
> 
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