I use Citrix Xenserver, and the VMs hard drives are LVM logical volumes, not
images sitting on a filesystem. I was not aware copy could do sparse files,
though, so thanks for the tip!
--
Robert A. Wicks
Systems Engineer
desk: (404) 888-2428
mobile: (404) 606-4622
rwicks@xxxxxxxxxxx
________________________________________
From: Brian Krusic [brian@xxxxxxxxxx]
Sent: Friday, March 20, 2009 5:22 PM
To: Robert Wicks
Cc: Xen-Users
Subject: Re: [Xen-Users] How to clone a VM when it is running?
Hi Robert,
Why do a dd when you can just cp or even cp --sparse=always?
Why restore to en empty VM when you can just use the copied image on a
different box?
Just tryin to see of I can adopt some techniques.
- Brian
On Mar 20, 2009, at 10:35 AM, Robert Wicks wrote:
FWIW, I have taken an LVM snapshot of a running Windows VM, done a dd out to a
file on an NFS mount point of the snapshot, and restored the resulting file
inside an empty, but identically sized VM on another Xenserver host without any
issues. The Windows box basically reacts like you just cut power. A checkdisk
is the worst which has happened, and I always have something I can use in the
output file. I wish there were a way to generate an XVA file from this output
so that I could just import the snapshotted backup as a normal Xen image.
Robert A. Wicks
ITC Engineer
desk: (404) 888-2428
mobile: (404) 606-4622
rwicks@xxxxxxxxxxx<mailto:rwicks@xxxxxxxxxxx>
From:
xen-users-bounces@xxxxxxxxxxxxxxxxxxx<mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx>
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Brian Krusic
Sent: Friday, March 20, 2009 12:40 PM
To: Nick Couchman
Cc: freddie weng; Xen-Users
Subject: Re: [Xen-Users] How to clone a VM when it is running?
Hi Nick,
I've experimented using LVMs and creating a snapshot volume of the root
partition where my vms live (/var/lib/xen/images).
You can then do whatever want with what's on the snapshot volume. So for
example. your virtual machine image is in a state in time when the snapshot was
taken.
Keep in mind that when you create a snapshot of VMware instances, it pauses the
VM before doing its thing.
When running popular cloning sw like Norton Ghost, etc... the machines state is
also fixed in time so I think you won't really be able to get around the
state-in-time/cloning thing.
- Brian
On Mar 20, 2009, at 8:35 AM, Nick Couchman wrote:
Cloning a VM while it is running isn't really a great idea. In order to
maintain filesystem consistency, at the time of the clone all filesystem
activity must be frozen and data needs to be flushed from the caches and
buffers out to disk devices. If order to do this while the VM is running, you
have to interact with the O/S of the VM to freeze filesystem transactions (XFS
is the only filesystem I've used that supports this), flush out the buffers and
caches ("sync"), then clone the disk image, then unfreeze the filesystem. A
much easier option is to pause the domU temporarily ("xm pause <domU>"), clone
it, then unpause.
Why is being able to clone while a domU is running so critical to you?
>>> On 3/20/2009 at 9:26 AM, freddie weng
>>> <freddieweng@xxxxxxxx<mailto:freddieweng@xxxxxxxx>> wrote:
Hi everybody,
I found that we can use virt-clone to clone a VM but only when that VM is not
running.
This is not useful most of the time.
Can we clone a VM even when it is running?
It's critical to my research, any idea is much appreciated!!!!
all the best,
Freddie
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