I know there have been many queries regarding backup, but this one is rather demanding. I should also mention that I've done a fair amount of googling, but was unable to find what I need.

I need a backup solution with the following features:

  1. backs up one or multiple hard disks as images to an external hard disk or NAS,
  2. supports block-level incremental backups,
  3. supports merging incremental backups into the full backup,
  4. automatically takes care of space on the backup medium by merging the oldest incremental backup into the full backup so as to make room for the newest incremental backup,
  5. operates from a preboot/live CD environment.


  1. after catastrophic events, I want to be ready to roll ASAP. Having to reinstall the OS and programs isn't conductive to that so file-based backup is out.
  2. Block-level saves space as opposed to file-level, and that enables me to fit more backups on the backup medium.
  3. This is crucial for #4.
  4. This seems like the best way for automatically managing the backups and free space on the backup medium considering that I just want to fit as much as possible and not worry about the details or do anything manually.
  5. This may seem odd, but it greatly decreases the chances of malware screwing up the backups. Consider: if you make backups from within your regular OS and it loses control to malware, said malware can screw up all of your backups if they're on a plugged-in external disk. If you use a NAS instead, it can screw up any currently-running backup by sending garbage to the NAS. Using a known-good live CD/PE on a read-only medium prevents this.

So, does this exist?

Edit: I forgot to specify that I need this for my home setup which consists of a few computers, including a laptop. Also realized that live CDs would be a better fit for #5.

1 Answer 1


Sure this exists, but you pay for it out the nose with performance.

Answer: Do this in a VM, or have the storage hosted on a SAN / network attached block device. With LVM you can get snapshots. How you store the snapshots is up to you, but I imagine you can find something that can do differencing like you describe. You may need to build it, but honestly that's not the part that seems overly challenging (binary differencing has been done before).

I think gPXE can do the booting / running entirely off of a SAN for you, and I think FreeNAS or other solutions can do the SAN. You put LVM between the disk and the exported SAN volume, and you can work magic.

Performance is the place I'd expect to pay a hit. Remote disks are going to be more expensive for the same performance.

  • Thanks for the answer, but after reading it I realized that I didn't specify that I need it for my home setup (edited now). If I needed this for a commercial purpose, your proposal would work very well. However, it's not very comvenient to boot a laptop off a SAN :) ; I guess I was getting at something more like a custom Linux distro that runs off a live CD. Also, performance isn't critical. Did you have any specific products in mind? Jul 22, 2011 at 21:39

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