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Re: [linux-lvm] Slow boot with large number of thin snapshots



On 02/07/2013 01:42 PM, Andres Toomsalu wrote:
Hi,

We have experienced a situation where we are left with large number
of thin snapshots (around 500) and snapshot removal wont work anymore
(we suspect a lock-up situation caused by trying to remove thin
snapshots that is still mounted - thou  its not verified yet - just a
speculation).  The only path to recover seems to be disabling all
thin volumes from fstab and booting into single-user mode - where
lvremove -f usually succeeds on these thin snapshots. But LVM init
and lvremove take a huge amount of time with large number of
snapshots  - initial LVM activation is going on about 6-8 minutes at
least and every lvremove takes ca 20-50 sec - depending on snapshot
count left. After snapshots are removed thin volumes can be enabled
again and fsck-ed and resuming normal operations.

Hello Andres, could you provide the following information:

Which version of lvm?
Is lvmetad used?

    grep lvmetad /etc/lvm/lvm.conf
    pgrep lvmetad

RHEL6.3 version of lvmetad had a serious performance issue with many [thin] snapshots, which should be solved in the latest release (lvm2-2.02.98)

Could you check the memory usage while the command is running?

Also there were a high memory usage problems fixed in the recent version.

-- Marian


Althou we are not yet sure what is causing the lockup - so that
snapshots cant be removed anymore without reboot - its also
problematic that with large numbers of snapshots all LVM device
operations are dead slow.  I hope this issue can be addressed somehow
in the future.

Kind regards,



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