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xen-users
Re: [Xen-users] Backup DomU volumes
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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