Some LVM tutorials seem to claim that one take a snapshot of a logical volume (LV), then backup the snapshot using another tool, then remove the snapshot. When the unspeakable happens, the user can restore their LV to the state it was during the backup.But how can this be? LVM snapshots are copy on write; they record changes to the state, not the state itself. If the snapshot is removed and changes are then made to the LV's state, these changes are not recorded; thus, the backup contains an incomplete record of changes to the LV during the attempted merge. So how can one expect their LV to be restored to the state it was during the backup?
How do backups that use LVM work?
backup;lvm;snapshot
I think you missed section '13.4.3. Do the backup'. LVM can be used to take a copy of the data at a point in time so you have a consistent** image of that data. As such, you can then use another tool (eg tar, fbackup etc) to do the actual backup. If you want to use LVM as a backup mechanism in itself, yes you do need to actually keep the LVM snapshot.** In the example the LVM snapshots appear (from the label) to be databases. Any application or database that is running on LVM should be stopped before taking the snapshot to ensure consistency (unless the database/application has support for LVM backups).