I found out some interesting things tonight. I removed my /var and /home snapshots, and all the corruption, with the exception of files I had changed while /var and /home were in their corrupted state, had disappeared! I overwrote several files on /var that were corrupt with clean copies from my backups, and verified that they were OK. I then created a new /var snapshot, mounted it, only to find out that the files on that snapshot were still corrupt, but the files under the real /var were still in good shape. I umounted, lvremoved, lvcreated, and mounted the /var snapshot, and saw the same results. Even after removing the snapshot, rebooting, and recreating the snapshot I saw the same thing (real /var had correct file, snapshot /var had corrupt file). Do you think my volume group has simply become corrupt and will need to be recreated, or do you guys think this is a bug in dm-snapshot? If so, please let me know what I can do to help you guys debug this. Thanks, Alex On Mon, 21 Feb 2005 15:18:52 +0000, Alasdair G Kergon <agk@xxxxxxxxxx> wrote: > On Sun, Feb 20, 2005 at 11:25:37PM -0600, Alex Adriaanse wrote: > > This morning was the first time my backup script took > > a snapshot since upgrading to 2.6.10-ac12 (yesterday I had taken a few > > snapshots myself for testing purposes, this seemed to work fine). > > a) Activating a snapshot requires a lot of memory; > > b) If a snapshot can't get the memory it needs you have to back it > out manually (using dmsetup - some combination of resume, remove & > possibly reload) to avoid locking up the volume - what you have to do > depends how far it got before it failed; > > c) You should be OK once a snapshot is active and its origin has > successfully had a block written to it. > > Work is underway to address the various problems with snapshot activation > - we think we understand them all - but until the fixes have worked their > way through, unless you've enough memory in the machine it's best to avoid > them. > > Suggestions: > Only do one snapshot+backup at once; > Make sure logging in as root and using dmsetup does not depend on access > to anything in /var or /home (similar to the case of hard NFS mounts with > the server down) so you can still log in; > > BTW Also never snapshot the root filesystem unless you've mounted it noatime > or disabled hotplug etc. - e.g. the machine can lock up attempting to > update the atime on /sbin/hotplug while writes to the filesystem are blocked > > Alasdair > -- > agk@xxxxxxxxxx >