Snapshots are amazingly useful. It's kind of hard to describe unless you see it. :) <br><br>I do the same thing here. My Backend runs in a Xen VM under OpenSolaris, so I just do a quick "zfs snapshot" on the Linux VM's zvol, do the upgrade, and if something breaks, I can revert to the snapshot and try again, or just wait for things to get more stable. If everything checks out, I can "zfs destroy" the snapshot to recover the space. Creating and destroying ZFS snapshots generally takes less than a second, so Ghost and similar tools can't touch the performance. And I can do it while the system is online. The guest VM hasn't the slightest idea I've taken the snapshot. Obviously, reverting to an old snapshot has to be done with the VM offline. <br>
<br>ZFS also lets me do the same thing to the OpenSolaris host OS. In fact, using "pkg" (aptitude in Solaris-speak) to upgrade the OS automatically handles this for me, and even adds the old versions to the Grub menu. So at boot, I can see a list of all the prior installs and boot into any of them without disturbing newer or older versions. Extremely handy if I mess something up. And I can mount any of the snapshots at any time to copy files to/from etc.. <br>
<br>Note that OpenSolaris does not do PCI passthrough, so this works for me because I don't do tuner cards. I have an HDHomeRun which doesn't require low level OS support. :) <br>