[linux-lvm] Cannot create more than 3 snapshots when system is busy

cfeng at plasmon.cn cfeng at plasmon.cn
Fri Apr 8 09:01:12 UTC 2005


Dear all,

       I have a problem with creating snapshots on the vanilla Linux2.6.11.5
kernel. I cannot create more than 3 snapshots on a logical volume when the
system is busy writing to the logical volume. When creating the fourth
snapshot the lvm.static just hangs there, and the process that writes data
to the logical volume also hangs. The system is still running though, and I
can access the system through ssh and do other things, but LVM subsystem is
hung. The filesystem on the logical volume is XFS and the physical volume
underneath is a RAID5. The following lines are from /proc/slabinfo which may
be useful:

 

dm-snapshot-in       128    140     56   70    1 : tunables  120   60    0 :
slabdata      2      2      0

dm-snapshot-ex    498095 498108     24  156    1 : tunables  120   60    0 :
slabdata   3193   3193      0

dm_tio             23549  52206     16  226    1 : tunables  120   60    0 :
slabdata    231    231      0

dm_io              23548  51754     16  226    1 : tunables  120   60    0 :
slabdata    229    229      0

 

       Has anybody seen similar problem? Any suggestion would be greatly
appreciated!

 

Regards.

Charles

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