This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] Xen & Automated Disk Management for Domains

To: Michael Vrable <mvrable@xxxxxxxxxxx>
Subject: Re: [Xen-devel] Xen & Automated Disk Management for Domains
From: Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>
Date: Thu, 05 Aug 2004 18:56:58 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxxx, Ian.Pratt@xxxxxxxxxxxx
Delivery-date: Thu, 05 Aug 2004 19:10:24 +0100
Envelope-to: steven.hand@xxxxxxxxxxxx
In-reply-to: Your message of "Thu, 05 Aug 2004 10:27:54 PDT." <20040805102754.A17452@xxxxxxxxxxxxxxxx>
List-archive: <http://sourceforge.net/mailarchive/forum.php?forum=xen-devel>
List-help: <mailto:xen-devel-request@lists.sourceforge.net?subject=help>
List-id: List for Xen developers <xen-devel.lists.sourceforge.net>
List-post: <mailto:xen-devel@lists.sourceforge.net>
List-subscribe: <https://lists.sourceforge.net/lists/listinfo/xen-devel>, <mailto:xen-devel-request@lists.sourceforge.net?subject=subscribe>
List-unsubscribe: <https://lists.sourceforge.net/lists/listinfo/xen-devel>, <mailto:xen-devel-request@lists.sourceforge.net?subject=unsubscribe>
Sender: xen-devel-admin@xxxxxxxxxxxxxxxxxxxxx
> One feature that would be really nice to have is the ability to easily
> manage the disk images used by the Xen domains, so that I could, for
> example, quickly load a particular Linux distribution on a set of LVM
> logical volumes, then start a new Xen instance with those.

I'd certainly like to see more support for this.

Copy-on-write (CoW) sparse disks are pretty high on everyone's
wish list. In principle, it should be possible to do this today,
but it's a pain to setup: use LVM snapshot with the log device as
a loop interface connected to a sparse file.

I've never actually tried this, but it should work. Has anyone?

[The LVM snapshot device is a bit 'odd' for our purposes as
writes occur in-place, with the old block contents being copied
to a log device. It would make more sense if we slightly modified
the code to have the writes go to the log and leave the original
device pristine. ]

It would certainly be very nice to have xend assist with setting
all this up, and have a nice way of naming images etc (leveraging
LVM wherever possible).
> This isn't terribly difficult to do with a few scripts running in Domain
> 0, and I already have a basic working version.  But as I'm looking at
> cleaning this code up, I'm wondering if it this functionality wouldn't
> be useful to others, and if it's worth integrating into the Xen control
> tools.
> Are there any current tools to do this sort of thing?  Any plans for
> such tools (in xend, the future Xen Cluster Daemon, or elsewhere)?
> Would it be worthwhile to try to make my code more general so that it
> could possibly be included in Xen?  Integration with xend/xm has some
> benefits:
>   - management over the network comes almost for free
>   - could integrate better with domain management; for example, it would
>     be easy to check that logical volumes for a running domain aren't
>     accidentally deleted
> On the other hand:
>   - perhaps there are already plans to accomplish this in some other way
>   - the persistence requirements for disk images are different than for
>     domains, and so there's not a perfect match
> Would anyone else find it useful if I worked on this?  If so, what features
> would you like to see?  Or am I going about this the wrong way?

xend is intended to be extensible for exactly this sort of
thing. Mike's writing a manual for it, which should be going into
the tree RSN.


This SF.Net email is sponsored by OSTG. Have you noticed the changes on
Linux.com, ITManagersJournal and NewsForge in the past few weeks? Now,
one more big change to announce. We are now OSTG- Open Source Technology
Group. Come see the changes on the new OSTG site. www.ostg.com
Xen-devel mailing list