Backing up live Xen!

Don't let the $0 price tag prevent you from doing awesome backups of your live Xen boxes.

Here's the quick primer before we eventually add all of the real details.  Your Xen (XenServer or open source) can be managed just like any linux logical volume based linux setup.  That means you can use the built in logical volume snapshotting.  You don't need fancy pants hardware (a $250,000 drive setup is always nice, tho!) or some unruly PoS backup package.

All you need are the regular tools from the command line and some thought.  Why isn't this exposed for you to use in all the nice GUIness that you paid for?  Why didn't they mention this in that 4 hour long marketing disguised as technical training seminar that you went to?

Your LV file system can be mounted by your Dom0 if it is ext3.  So, why can't you just back it up from there?  Well, you can.  Just snapshot the logical volume you want to backup, mount the snapshot, and back it up.  Nothing special to see there except you have a backup of your stuff without loading annoying backup drivers or without taking your system down.

Watch out, however, you're backing up a system in a live state, if you have open databases, you're backing them up open, so they won't be consistent if you restore and you'll have to roll logs or break out the voodoo.  Be sure to dump databases to disk before the backup, or if you can afford a very short reboot, shut the system down, snapshot, and bring it back up.  Your snapshot will be of the system in a powered down state -- the best state to get a backup from.  Even better, you can backup everything using rsnapshot and rsync so you only have to store your deltas if you do the job right.

Your Windows system is a different story.  You can do a block level backup of the snapshot easily enough.  We're working on a scheme to get NTFS mounted in the same way you can mount ext3.  More news on that to come.  Also, the actual commands coming soon for linux too..

Mounting RAW files that have LVMs inside them -- random info needed while I'm working on making a backup system