Filesystem backup: copy configuration

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#1 Sat, 01/31/2009 - 02:39

Filesystem backup: copy configuration

I do have a question regarding Webmins Filesystem Backup feature. I configured it using dump to weekly doing a full backup and daily an incremental backup. Once it is running on a 2 CPU XEN guest the load is jumping up to 3. That's on a machine used for web and email hosting.

Although it probably is no big problem having a load of 3 I rather would avoid it. My idea is to let a second XEN guest doing the backup by creating a LVM snapshot volume of the hosting volume and backing up data from the snapshot volume. This also has the advantage of non changing data during the backup process. The second XEN guest is configured to use fewer CPU resources so it hopefully may not affect the first XEN guest much. So far so good.

Question is: Can I copy the backup configuration created on the first XEN guest to the second one?

The second XEN guest is not running Virtualmin because I don't want all the features like Apache, database etc. on that machine. May be I'm trying to be too puristic in that point? Shall I just install Virtualmin or Webmin only there and being happy to use the Webmin GUI? What do you think?

Sat, 01/31/2009 - 07:38


Please correct me if I'm wrong - do you want to have a second domU only for doing backups from the domU where Virtualmin is installed? If you do, I suggest not to follow this direction. First of all load of 3 is nothing you should be worry about when the backup is in progress. The second thing, why boder with the second domU, you may do backups from the dom0 (without virtualmin). Maybe I'm not very familiar with XEN, but is it possible to do snapshots of one domU within another? It would be the violation of the virtualization concept.


Mon, 02/02/2009 - 07:22

The second domU is running anyway - it is doing Spamassassin and ClamAV filtering for the domU used for web and email hosting. I had bad experiences in the past when some SPAM peaks did slow down the web hosting stuff so I offloaded that part to a lower prioritized domU.

You are right: You can not do snapshots of one domU within another domU. But you can SSH from a domU to the dom0 and do the snapshot there of course. After that you just have to attach the created snapshot device to the domU and mount it there. After the backup you unmount it in the domU, deattach it from the domU and remove it as logical volume on the dom0.

Because the deattaching is broken currently in XEN 3.0.3 I decided to run the complete backup process on the dom0. Don't know yet how this affects the performance of my domU's though. But running the backup on the dom0 using LVM snapshots is a clean process at least.

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