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Re: [Xen-users] Multiple Domains Sharing Root System

To: chris@xxxxxxxxxx
Subject: Re: [Xen-users] Multiple Domains Sharing Root System
From: Marcus Brown <marcusbrutus@xxxxxxxxxxxxxxxx>
Date: Tue, 20 Sep 2005 19:25:54 +1000
Cc: mark.williamson@xxxxxxxxxxxx, xen-users@xxxxxxxxxxxxxxxxxxx
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Hi Chris,

Chris de Vidal wrote:
> --- Marcus Brown <marcusbrutus@xxxxxxxxxxxxxxxx> wrote:
> 
>>My plan is to have an NFS root server as a domain, using multiple LVM
>>partitions. (I could run it in dom0 if required).
>>Using a UnionFS-patched kernel I hope to combine a (writable) domain-
>>specific partition with a (read-only) generic image for each domain.
>>This would allow each domain to have custom configs and apps.
> 
> 
> As I was contemplating with the COW filesystems, wouldn't a UnionFS over time
> grow to be about the same size as if you'd have done individual installs?
> 

I think there is a fundamental difference here in each approach.
With a COW system (eg. LVM snapshots?) I'd imagine each system needs
to be updated independently ... ie. each domain would grow away from
it's origin. I can't see re-merging data common to all domains being
an easy task.
With my NFS suggestion however, the generic image itself can be
updated ... hence the saving. ie. master updates/upgrades are done
on the generic image, and then each domain can have it's specialised
updates separately.

Marcus.

ps. Having sanity problems trying to compile unionfs for a Xen kernel. :)

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