
James Harper wrote:
I have a windows VM running under Xen, and want to take snapshots of all the LV's it is using as it's physical disks, eg:
vg0/lv0 - OS vg0/lv1 - FILESTREAM data vg1/lv2 - Databases vg2/lv3 - Database Logs
vg's 0, 1, and 2 are on different sets of spindles to give higher IOPS. The problem is that the 4 snapshots need to be created atomically or else I'm going to get my database and transaction logs out of sync as there could be a few ms between the snapshot of lv2 and lv3.
AFAIK you can't do that. In IIRC Scalix there was an option to say "get your shit in order and be quiescent until further notice, or fifteen seconds, whichever elapses first." Then you'd make your snapshots, then (since it was probably <<15s) say to scalix "OK, you can buffer writes again". I have no idea how well that actually worked, since I (thankfully) never had to restore that box from backups. Plan B, of course, would be to dump the database, then backup that.