[mythtv-users] MythTV 0.23 Available

Travis Tabbal travis at tabbal.net
Tue May 11 18:16:47 UTC 2010

Snapshots are amazingly useful. It's kind of hard to describe unless you see
it. :)

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.

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..

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. :)
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