[linux-lvm] Creating snapshot on / hangs machine

[Kai Leibrandt]

Hi all,

I am not sure if this should even be possible, but in order to take 
consistent backups I would like to take a snapshot of my / filesystem, and 
then use dump for the backup, but this consistently hangs my machine. My box 
is Fedora Core 2, kernel 2.6.8-1.521, lvm2-2.00.15-2, the filesystems are:

/boot: ext3 on /dev/md0
/: ext3 on /dev/VG00/RootLV on /dev/md1
/export: ext3 on /dev/VG00/ExportLV on /dev/md1
swap: swap on /dev/VG00/SwapLV on /dev/md1

VG00 has 500Mb free, and the snapshots I create are of the right size 
(lvcreate -L500M -s -n BackupLV /dev/VG00/ExportLV for instance). Taking 
snapshots  on /export is fine, and I have done some stress testing on this, 
repeatedly creating snapshots, dumping the snapshot to file, removing 
snapshot, etc. As soon as I create a snapshot on / however, the machine 
hangs, although X still works (well, the mouse still moves), it is no longer 
possible to open a new shell, switch consoles, or even <CTRL>C the lvcreate.

I have tried this with ext2 as well as with xfs, including doing xfs_freeze 
before taking the snapshot, so I don't think it's a filesys related matter.

Is there anything I am missing here? Is it even supported to do / snapshots?

Many thanks for any help,

Kai.

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