[linux-lvm] snapshot creation fails (in some cases)

[Jens Potthast]

Dear list,
Since I couldn't find any clue to what is wrong with my system (or
lvcreate?) [searched list archives, Google, how-to] someone reading this
list might be able to help me or give me a hint.
The Problem: Creating snapshots will fail under certain circumstances: a)
the snapshot is > 512MB (fails in aprox. 99.9%), b) the snapshots is < 512MB
(fails in aprox. 0.1%). I can't figure out, why creating of >512MB snapshots
in rare cases does not fail.
# lvcreate -L516M -s -n mysnap /dev/system/lv_home
  LV system/mysnap in use: not removing
  Couldn't deactivate new snapshot.

/dev/sysem/ shows mysnap. But I can't mount it (mount: filesystem unknown).

# lvdisplay
  --- Logical volume ---
  LV Name                /dev/system/mysnap
  VG Name                system
  LV UUID                LUVE4M-wC4g-YqhI-2gw4-wgfq-P2G0-2k82Ih
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                516,00 MB
  Current LE             129
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:7

Executing lvcreate -vvv does not help. Syslog might be of help: if creation
fails, I only get one entry:
/etc/hotplug.d/block/50-hwscan.hotplug[16398]: new block device /block/dm-7

If creation does not fail, it will show up four entries:
/etc/hotplug.d/block/50-hwscan.hotplug[16540]: new block device /block/dm-7
/etc/hotplug.d/block/50-hwscan.hotplug[16582]: new block device /block/dm-8
/etc/hotplug.d/block/50-hwscan.hotplug[16621]: new block device /block/dm-7
/etc/hotplug.d/block/50-hwscan.hotplug[16611]: new block device /block/dm-9


My distribution: SuSE 9.3 on two S-ATA drives.
If I can give any further information, please let me know.

Thanks in advance.

	Jens Potthast