RE: [Xen-Users] How to clone a VM when it is running?

[Robert Wicks <rwicks@xxxxxxxxxxx>]

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

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rwicks@xxxxxxxxxxx

 

From: 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> 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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