It sounds like the module needed by device-mapper to support snapshots
is not loaded when it is needed. (Perhaps the module - dm-snapshot -
is not in your initrd image?)
After step 3, but before step 4, try doing a 'dmsetup table' to see if
things are properly mapped. A 'dmsetup status' wouldn't hurt either...
Certainly, there should never be a kernel oops... It's tough for me
to say whether this bug is already fixed - given the age of your kernel.
brassow
On Jul 1, 2008, at 4:10 PM, Rob West wrote:
Does anyone know of ways that snapshots can become invalid other
than by writing more to the origin than the COW device can hold?
The reason I ask is that we're having cases where a snapshot is
becoming invalid, but we are very skeptical that it is due to
overfilling. The size of the origin is 83G, and the size of the
snapshot is 8G.
Here's what little we can tell from the logs:
1. Backup script creates a snapshot and starts copying data from it.
2. Before backup is finished (and thus, snapshot removed), the user
reboots.
3. On reboot, we get the following message which seems to be normal
for this kernel:
kernel: device-mapper: table: 253:2: snapshot-origin: unknown
target type
4. About 23 hours later, the backup script tries to create the
snapshot again but fails b/c it's still there.
5. The backup script tries to clean up by removing the snapshot, but
lvremove causes a kernel oops because the snapshot is invalid. (We
have identified a potential patch for this, but are trying to figure
out why the snapshot was invalid in the first place.)
The kernel we're using is based off of Fedora 6 (2.6.18-1.2849).
Not sure whether it matters, but device-mapper is version 1.02.07
release 4.0.RHEL4 and lvm2 is version 2.02.06 release 6.0.RHEL4.
Thanks for any help,
Rob
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