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Re: [Xen-users] what to backup Xen partition with?

  • To: "JHJE (Jan Holst Jensen)" <jhje@xxxxxxxxxxxxxxx>
  • From: Nico Kadel-Garcia <nkadel@xxxxxxxxx>
  • Date: Fri, 02 Feb 2007 08:23:41 +0000
  • Cc: "Rakotomandimby \(R12y\) Mihamina" <mihamina.rakotomandimby@xxxxxxxxxxxxxxxxxxx>, Xen-users@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Fri, 02 Feb 2007 00:23:20 -0800
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JHJE (Jan Holst Jensen) wrote:
I have 4 x 10GB to backup. Of course, the backup is done while the domains are down.
The domains are 4 different Linux distributions I make tests on.
But it's still too slow (dd+bzip2). Would you know another way to make partition backups?


Since these are all Linux distros, AND you are backing up while the
domains are down, I would suggest that you simply mount the partitions
and do a tarball of the file system - or do an rsync of the whole thing
for even better performance.
dd will always be slow and oversized! You have to read every single byte, and if you're writing to a file on the same disk, the disk is going to be chugging back and forth even worse. Even on another disk, it's hardly efficient. And if it's a live file system, you're in danger because it's possible, even likely that blocks will not yet be written to disk and you can have an extremely corrupt filesystem recorded without the information to fix it.

So don't do partition backups. Store a note about the size and location of the partition, a note about the type of file system, then mount it and do a tarball of the files. There are techniques to make a file-system snapshot and a "paused" copy of the Xen domain that may also help: snapshot it and build a new domaiun frm the copy, then shut the copy down and make a tarball from *that*. It'll also restore to a new partition a lot faster than a dd copy, and you can use a different sized partition for the newly restored domain if desired.

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