CentOS - Dec 2007 - building a Xen guest image on straight LVM partitions?

Hello,

When I needed to build Xen guests under Debian I could follow more or
less the instructions in http://preview.tinyurl.com/2oc48r and the
advantage of this approach is that it allows me to setup the Xen guest
directly on the LVM partition without making it consider the LVM
partition as an entire disk with a partition table.

The advantages of this approach are:
1. I can add more LVM's later, or share LVM's at the host level among
multiple Xen guests.
2. I can easily grow/shrink the Xen guest's disks.
3. I can access the Xen guest's filesystem much more easily
5. Probably less overhead in having LVM->parition->LVM.

But I didn't find a way to achieve this with CentOS 5's automatic
tools. Is this supported by CentOS as a Xen host or do I have to find
my own way?

Thanks,

--Amos

Monday 10 December 2007 04:50:04 Amos Shapira
napisa?(a):
> Hello,
>
> When I needed to build Xen guests under Debian I could follow more or
> less the instructions in http://preview.tinyurl.com/2oc48r and the
> advantage of this approach is that it allows me to setup the Xen guest
> directly on the LVM partition without making it consider the LVM
> partition as an entire disk with a partition table.
>
> The advantages of this approach are:
> 1. I can add more LVM's later, or share LVM's at the host level
among
> multiple Xen guests.
> 2. I can easily grow/shrink the Xen guest's disks.
> 3. I can access the Xen guest's filesystem much more easily
> 5. Probably less overhead in having LVM->parition->LVM.
>
> But I didn't find a way to achieve this with CentOS 5's automatic
> tools. Is this supported by CentOS as a Xen host or do I have to find
> my own way?
As far as I know it's not supported with standard CentOS tools. 

pz
-- 
Tomasz Napierala
System Administrator
QXL Poland - Allegro.pl Team
http://www.allegro.pl/

Amos Shapira wrote:
> When I needed to build Xen guests under Debian I could follow more or
> less the instructions in http://preview.tinyurl.com/2oc48r and the
> advantage of this approach is that it allows me to setup the Xen guest
> directly on the LVM partition without making it consider the LVM
> partition as an entire disk with a partition table.
I might be missing something, but that link seems to talk 
about FAI and doesn't mention xen. I'm interested in seeing 
how it can install on the LVM partition but the OS doesn't 
see it as an entire disk with a partition table. What does 
"fdisk -l" show, then?

johnn

Amos,

The quickest way to deploy a Xen VM requires a little more prep work...

Use the regular (long) method as discussed. Most use an HVM to do the install
but config it as a domU afterward as most installers only work reliably in a
fully virtualized environment.

Create an LVM based guest for each distribution/OS you plan to use. Then for
each Xen guest you want to create take an LVM snapshot of the distribution/OS of
choice and use that for the guest.

This way guest deployment is very quick and disk space is conserved wisely. You
can start with 1 or 2 GB snapshot and as space gets tight in the snapshot add
more storage.

-Ross


-----Original Message-----
From: centos-bounces at centos.org <centos-bounces at centos.org>
To: CentOS mailing list <centos at centos.org>
Sent: Tue Dec 11 01:50:01 2007
Subject: Re: [CentOS] building a Xen guest image on straight LVM partitions?

On 11/12/2007, Ross S. W. Walker <rwalker at medallion.com>
wrote:
> Here is a good link: http://wiki.rpath.com/wiki/Xen_DomU_Guide
Ah and forgot to say "thank you" for the link. Looks useful.

Cheers,

--Amos
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