[linux-lvm] F7 will not boot after running backup w/snapshot

[Mikulas Patocka]

On Thu, 1 May 2008, Gerry Reno wrote:

> Mikulas Patocka wrote:
>> ... If you mount the origin device with missing snapshot, you destroy the 
>> snapshot (even if you don't touch it). The snapshot can no longer be 
>> repaired.
>> 
> So it is safer to not activate device in this case then destroy data.
> Why? What value is the old snapshot at this point? You just had a system 
> reboot in the middle of a snapshotted backup so all you need to do is get the 
> system up, redo another snapshot and retake your backup. I'm not interested 
> in the old snapshot.

If you use snapshots for something other than backups (for example 
version-control using snapshots --- to enable admin to revert changes if 
he messes something), then the snapshot is valuable and should survive 
reboot.

Anyway, placing a ramdisk to volume group is bad idea and it must not be 
done on any production system --- note that any lvcreate, lvconvert, etc 
command can allocate anything on that ramdisk --- without the 
administrator knowing it.
--- so I don't see any reason why we should do extra hacks to lvm for 
people who placed ramdisk into vg.


To use temporary storage for snapshot, a special command for lvm would be 
more appropriate --- a command that would setup snapshot and write nothing 
about it to metadata, so that the snapshot would be forgotten on next 
reboot --- then, you can setup the snapshot on any device outside the 
volume group. You can already do this with dmsetup.

Mikulas