I read a description of a very intriguing backup strategy that seems to fit my requirements. I need help to:
- implement it manually one time
- automate it to run periodically
Here's the original article describing the concept:
Here's my situation:
- home file server with about 1.2 TB of stuff to be backed up
- external 2.0 TB USB drive available to hold all the backed up stuff
- another external 2.0 TB USB drive available, if needed.
- images of root, /home and /var in the form of LVM logical volumes that are ready to mount at restore time. (I plan to snapshot these LVs and backup while the server is running.)
- image of /boot (which is not an LVM LV and which I assume doesn't need to be snapshotted anyway as it won't be changing)
- copy of MBR (I have a simple script for making incremental copies)
- file-based backups of non-LVM paritions containing media --music, video, documents, etc.(I will use storeBackup for this, which is like rsync but it finds duplicates by content rather than just file name)
What I'm looking for is a step-by-step recipe similar to the source article style, but applicable to my situation.
Some initial questions are:
- should I prepare the external 2.0 TB USB drive with 1 standard partition or should I use LVM (maybe with 1 vg and 1 or more logical volumes)?
- is LVM mirroring a reasonable way to initially duplicate the logical volumes onto the external 2.0 TB USB drive? If not, what's the best way to copy the source logical volumes to the external drive and end up with ready-to-use logical volumes? Mirroring seems crucial to this strategy because (I hope) it will avoid requiring future periodic full copies of the source LVs. (But that's only a hopeful guess.)
- Once the logical volume copies are in place on the external drive, can I take snapshots of these backup LVs?
- Assuming I can snapshot the backed up LVs, at the next period backup from source, can I quickly sync the copy then take another snapshot? The idea I'm going for is to:
- establish the LV mirror on the external drive
- make a post-backup snapshot of the LV on the EXTERNAL DRIVE
- break the link between the mirrored LVs
- after a week, resync the mirror (should involve just copying changed blocks, I hope)
- make another post-backup snapshot of the LV on the EXTERNAL DRIVE
- again, break the mirror so that the source file system is not doing any copy-on-write, etc.
- pre-backup snapshots: these are ordinary LVM snapshots used in the traditional manner
- post-backup snapshots: these are intended to be permanent references to earlier points in time in the "backup series".
- backup series: a "mirror" of the source logical volume together with periodic snapshots that are retained indefinitely.
I've never used LVM snapshots before!