Hello!
We see significant performance issues with the LVM RA when writing to an ext3
filesystem with default journaling and berriers enabled. So anything that
speeds up the RA monitor operation (it needs up to 90 seconds here
accasionally) would be appreciated.
However I feel the best thing would eb to fix the perfomance issues in the LVM
commands, rather than not using them.
For the vgck: If the VG metadata are checked during startup, a periodic
re-check seems unnecessary to me: During normal (use) operation of the VG's LVs
(that's the typical use case for VGs in a cluster configuration) the
(checkable) metadata don't change a lot, so it may not make much sense. I'd
rely on the kernel to shutdown (i.e. put into read-only) a faulty VG anyway.
The paranoid should monitor individual LVs anyway instead of just monitoring
the VG.
Eventually the documentations says:
"The 'monitor' operation reports whether the volume seems present"
So probably a [ -r /dev/mapper/VG-name ] should also do ;-)
I see that vgck is used even after LVM_status was successful; LVM-status uses
vgdisplay to check the status. There's another funny thing in my version
(SLES11 SP1): The check is:
vgdisplay -v $1 2>&1 | grep -i 'Status[ \t]*available' 2>&1 >/dev/null
but there is not "available status" for the VG, only for the LV!
# vgdisplay -v VG |grep Status
Using volume group(s) on command line
Finding volume group "VG"
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
Do not wait for udev on information only command
VG Status resizable
LV Status available
LV Status available
PV Status allocatable
So the VG is not "available", but "resizable". Well, there are many ways to
write a resource agent, but only few of them are correct...
Regards,
Ulrich
>>> "Xin Wei Hu" <[email protected]> schrieb am 14.11.2011 um 10:00 in Nachricht
<[email protected]>:
> Hi all,
>
> Here attached a patch, to remove vgck in the LVM RA completely.
>
>
> As we know, the LVM RA's used to provide a working VG for others to use.
> However, vgck is a tool to check the metadata consistency across all
> physical volumes. So, it can be the case that the VG is living and
> everything's
> fine, but the metadata is in-consistent on physical volumes. This can be
> found oftentimes on mirrored VG.
>
>
> So I proposed to drop vgck in the RA completely, for
> 1. avoiding the false alarm by vgck
> 2. performance imporoving vgck is time and disk consuming cause it scan
> all physical volumes for metadata.
>
>
> Please let me know if you have concerns on this.
>
>
> Thanks.
>
>
>
>
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