[Linux-HA] Antw: Re: ocf::LVM monitor needs excessive time to complete

[Ulrich Windl]

Hi!

I wonder: What is the preferred way to select the correct devices for LVM in a SAN multipath environment where the names change a lot? There are /dev/sd*, /dev-dm*, /dev/mapper/*, dev/disk/by-*/*. What I don't want is to change the list after each change to the LVM configuration.

Regards,
Ulrich


>>> Vladislav Bogdanov <bubble at hoster-ok.com> schrieb am 20.08.2011 um 23:07 in
Nachricht <4E502227.2010102 at hoster-ok.com>:
> 05.08.2011 14:55, Ulrich Windl wrote:
> > Hi,
> > 
> > we run a cluster that has about 30 LVM VGs that are monitored every
> > minute with a timeout interval of 90s. Surprisingly even if the system
> > is in nominal state, the LVM monitor times out.
> > 
> > I suspect this has to do with multiple LVM commands being run in parallel 
> like this:
> > # ps ax |grep vg
> >  2014 pts/0    D+     0:00 vgs
> >  2580 ?        D      0:00 vgdisplay -v NFS_C11_IO
> >  2638 ?        D      0:00 vgck CBW_DB_BTD
> >  2992 ?        D      0:00 vgdisplay -v C11_DB_Exe
> >  3002 ?        D      0:00 vgdisplay -v C11_DB_15k
> >  4564 pts/2    S+     0:00 grep vg
> > # ps ax |grep vg
> >  8095 ?        D      0:00 vgck CBW_DB_Exe
> >  8119 ?        D      0:00 vgdisplay -v C11_DB_FATA
> >  8194 ?        D      0:00 vgdisplay -v NFS_SAP_Exe
> > 
> > When I tried a "vgs" manually, it could not be suspended or killed, and it 
> took more than 30 seconds to complete.
> 
> You just need to filter unneeded block devices (or leave only needed)
> from LVM "suspects to be PV". Otherwise LVM tries to open every LV to
> look if it is PV. Look at /etc/lvm/lvm.conf for "filter" line.
> 
> BTW under very high CPU/IO load I found that "chrt -r 99" helps LVM
> utils to work much faster. Combining this with "timeout" utility (to
> prevent that LVM utils from "never-finish") does some more magic.
> 
> Best,
> Vladislav
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