From:
xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Grant
McWilliams
Sent: Monday, August 04, 2008 7:17 PM
To: Javier Guerra
Cc: Chris Edwards; Michael March; xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen Image File vs LVM
On Mon, Aug 4, 2008 at 1:04 PM, Javier Guerra <javier@xxxxxxxxxxx> wrote:
On Mon, Aug 4, 2008 at 3:01 PM,
Michael March <mmarch@xxxxxxxxx>
wrote:
>>
>>> 3. If I have a xen guest os in a LV how
would I migrate the guest os
>>> from one machine to the other? Create identical LV on new
machine?
>>
>> to migrate VMs, the storage has to be accessible from both machines
>> with the same reference. when using image files, that means a
shared
>> filesystem (NFS, GFS, OCFS, etc.), when using LVs, that means the VG
>> must be accessible from both hosts, usually with a SAN or SAN-like
>> setup (FC, iSCSI, drbd, AoE, (g)nbd, etc)
>
> Is this for 'live' migrations or any migration of a VM?
sorry, didn't read the whole question.
this is for live migrations. for 'manual' migrations, you can get by
copying the data (and i guess you could also migrate between image
files and LVs, but i haven't tried that (yet))
--
Javier
You can go between LVs and files too really easy. I've started putting
tutorials up on these things as I get to them at http://grantmcwilliams.com/index.php?option=com_content&view=category&id=97&Itemid=379
The URL will be changing though as I implement SEO on my site.
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How to move from a tap:aio file to Logical Volume Management
In Xen we can provide virtualized hard drives several different ways. It's
not uncommon to create a large empty file using dd and then specify it as the
hard drive like this.
name = "mailserver"
memory = "1024"
disk = [ 'tap:aio:/srv/xen/mailserver.img,xvda,w', ]
vif = [ 'bridge=xenbr0', ]
bootloader="/usr/bin/pygrub"
vcpus=2
In this example /srv/xen/mailserver.img is our file. In a lot of ways LVM is
more powerful and faster so moving our test server to LVM makes sense once
we've gotten serious about deploying it. Moving from tap:aio to LVM is much
easier than you think, here's how.
1. Shutdown domain.
xm shutdown mailserver
2. Create the Logical Volume
You'll need a Logical Volume the same size as your Xen disk file. In this
example the Xen disk file is 10GB and I'll assume you already created it. This
could easily turn into an LVM tutorial if I don't.
10 GB Disk file: /srv/xen/mailserver.img
10 GB Logical Volume: /dev/VolGroup00/LogVolMAIL
3. Copy disk file to Logical Volume
dd if=/srv/xen/mailserver.img of=/dev/VolGroup00/LogVolMAIL -bs 1024
4. Edit the Xen domain config file
name = "mailserver"
memory = "1024"
disk = [ 'phy:/dev/VolGroup00/LogVolMAIL,xvda,w', ]
vif = [ 'bridge=xenbr0', ]
bootloader="/usr/bin/pygrub"
vcpus=2
5. Restart domain
xm create -c mailserver
