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xen-users
Re: [Xen-users] Backup DomU volumes
Hi Pavel,
Please read LVM Howto for understanding howto LVM snapshots works
http://tldp.org/HOWTO/LVM-HOWTO/snapshots_backup.html
making a snapshot is quite easy & quickly, making the backup (rsync,
tar, bacula,....) isn't quickly :( and its the most horrible part in the
sysadmin life...
Regards,
Marc
Pavel Georgiev wrote:
Sounds about right, except that it will probably take too much time to make
snapshots of 270GB volumes. How long would that take and how much space would
it require.
On Tuesday 02 October 2007 16:57:26 Marc Patino Gómez wrote:
Hi Pavel,
In my opinion, using LVM will help you. When you want backup a running
VM which his VBD is on a LVM volume you can make a snapshot, then mount
the snapshot, after this, make the rsync and finally remove the snapshot.
Best regards,
Marc
Pavel Georgiev wrote:
Hi List,
I`m trying backup the volumes of VMs running on a xen server (3.1). I`ll
backup ext3 and reiserfs volumes. My goal is to backup them from Dom0 so
that I can avoid messing with DomU (adding scripts, cronjobs etc.). I
have another server running xen and I plan to keep exactly the same
volumes on it so I can start the VMs on this server in case my main
server dies.
The way I see it, I`ll be mounting volumes on both servers and
doing 'rsync -avP' on the content (in order to avoid transferring already
existing file). The problem (maybe not a problem of xen, but I guess
other people have bumped into this) is how do I mount volumes without
stopping the VMs and without corrupting the data on the volumes.
When a volume is in use by a VM, it either has the "need_recovery" flag
(ext3) or cannot be mounted ro (reiserfs). I could remove the
"need_recovery" flag for ext3 volumes and mount them read-only, do the
sync and then umount and set the flag again. For reiserfs I could mount
the volume read-write, remount read-only and then do the sync. Are those
two approaches safe? Is this going to corrupt my volumes, after all I`ll
do some writing (removing the flag for ext3 and replaying the journal for
reiserfs)?
In general, what are my options if I want to copy the volumes to another
server (hopefully only the changed files) without stopping the VM. The
rsync does not have to be atomic, it is OK if DomU writes some data after
I start rsync.
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