2009/12/12 Christopher G. Stach II cgs@ldsys.net:
----- "Kenni Lund" kenni@kelu.dk wrote:
I'm also very interested in how to make backups of Windows guests on LVM. But will the shadow copy feature in amanda not only backup the files within the Windows machine? I don't think I fully understand the method - How do you then do a full restore, eg. with no working Windows machine? Would you then have to do a clean install of Windows in order to get the partition and bootloader setup correctly, after which you can do the restore by overwriting all files?
You can just shut down the VM, make a snapshot, start the VM, dd the snapshot, and finally drop the snapshot.
Or, if that's too much downtime, you can xm save, snapshot, copy save dumpfile, xm restore, dd snapshot, backup dumpfile, and clean up.
If that's too much downtime, you can xm pause, snapshot, xm unpause, etc., but you will have issues with your restore because it will look like the VM crashed and you may or may not lose data.
Yeah, that's the problem. AFAIK if I want to take advantage of using LVM directly for Windows guests, I'll have to do a full dump with dd of the image/snapshot, including any unused bits...eventually combined with some compressing, but still. If I use a Linux filesystem on top of LVM and store the Windows guest in an image on this filesystem, the overall I/O performance will be lower, but I'll only have to backup data which are actually in use, due to sparse mode and/or the qcow2 image format (I'm using KVM). This is quite relevant if some machines have 200GB allocated HDD space, but only actively uses 30GB.
Personally, I only back up data and never have useful data on a Windows installation volume (or even a native Windows volume, if I can help it). I can reimage a Windows machine with a single command and it only takes a few minutes. (Hint: use Sysprep.) Besides, reinstalling Windows machines is better than restoring them since they progressively bit rot.
I agree, I already have backups of the important data, but some of these machines runs some old legacy software, which I for sure don't want to setup again unless it's extremely critical. Also, what I want is a minimal monthly full backup of each virtual machine, from which any of my (less technical) colleagues can restore to another physical server by following some simple guidelines.
I think I'll stick with the extra layers (filesystem+image) for now to keep the setup simple and to keep the backups small. But thanks for your input.
Best Regards Kenni Lund