Re: [Xen-users] Shared storage in Xen Cluster

["chetan saundankar" <chetan.lists@xxxxxxxxx>]

Thanx Sven,

1. I would have liked to have a non intrusive solution for
implementing COW but it seems that for the time being I need to
install COW capable drivers in domU which means when I try to deploy
guests in automated fashion, I will have to carry out something like
remote installations into guest domains which is going be a tedious
task as there are no standard API's for such a task (or is it there?
if no error/exception handling is a worry)

2. COW for HVMs as you said is distro specific, which means storage
optimization using COW for deploying Windows guests is not possible.

3. You have also stated in your mail that performance of guests within
COW solutions suffers to an extent. I would like to have more pointers
on this performance issue and if there are any optimizations that can
be done in order to achieve a better performance.



On Jan 4, 2008 4:35 PM, sven waeyenbergh <sven.waeyenbergh@xxxxxxxxx> wrote:
> Chetan,
>
> answers below
>
>
> On Jan 4, 2008 11:47 AM, chetan saundankar <chetan.lists@xxxxxxxxx> wrote:
> > Hi Sven,
> > Thanks a lot for replying. Yes I am looking for the solution that you
> > have described in your mail.
> > Now I would like to know couple of things regarding COW,
> >
> > 1. Is there any requirement of installing any package or updating
> > configurations within the guest VM? if yes is there any work around.
>
> Yes, you will have to install COW-capable drivers on domU. There are several
> different possibilities, they are listed on the link in my previous mail. I
> think the best option is o use this one :
> http://wiki.xensource.com/xenwiki/InstructionsFromMichaelLang
> That one uses unionFS. I think that is available from the standard redhat
> distribution.
>
> >
> > 2. How to deploy Fully Virtualized guests in the COW fashion?
>
> i doubt very much that this is possible on HVM domains. The question if this
> is possible or not is actually more dependant on the distribution that you
> will use on domU than on xen itself. If you choose a distribution that can
> be installed on a COW filesystem, it should also be possible in xen. I
> personally think a redhat system is the best choise, ince there are a lot of
> readme's for redhat out there.
>
>
> >
> >
> > Regards
> >
> > Chetan
> >
> >
> >
> >
> > On Jan 4, 2008 3:50 PM, sven waeyenbergh <sven.waeyenbergh@xxxxxxxxx>
> wrote:
> > > It sounds like you need a COW filesystem.
> > > COW stands for copy on write. This means that you have a single root
> > > filesystem that is shared by all guests, and each guest has an extra
> volume
> > > that he will use to write any changes to (instead of the root
> filesystem).
> > > it's a bit like a snapshot works.
> > > This enables you to have a single image for multiple machines, and you
> can
> > > even have local changes for each machine.
> > > Note that this will be a very bad idea if performance is important to
> you.
> > >
> > > I'm sure this worked with xen2.0, i'm not sure of the support on xen
> > > 3.0/3.1, but you should be able to find more info here:
> > > http://wiki.xensource.com/xenwiki/COWHowTo
> > >
> > > S
> > >
> > >
> > >
> > >  On Jan 3, 2008 11:35 PM, chetan saundankar <chetan.lists@xxxxxxxxx>
> wrote:
> > > >
> > > >
> > > >
> > > > Hi all,
> > > > I am having following deployment scenario,
> > > > - 2 Xen hosts (running Xen 3.1)
> > > > - 1 Image server (NFS)
> > > >
> > > > Requirements:
> > > > -----------------
> > > > 1. Have an file system image of a linux distribution say Fedora 8 on
> > > > Image (NFS) Server
> > > > 2. I want to have 4 guests running Fedora 8 but for 4 different users.
> > > > 3. Base file system image (Fedora 8 image on Image server) shared
> > > > amongst 4 users in Read only fashion
> > > > 4. All 4 users will have separate VBD's for user specific data.
> > > >
> > > > Question:
> > > > ------------
> > > > Is there any way to force users write on the data VBD's exported for
> > > > each VM?
> > > > The whole point is that guest user should not worry about where to
> > > > write, every write call should be targeted towards data VBD and this
> > > > needs to be achieved without changing anything in the guest.
> > > >
> > > > Thanks and Regards
> > > > Chetan
> > > >
> > > > _______________________________________________
> > > > Xen-users mailing list
> > > > Xen-users@xxxxxxxxxxxxxxxxxxx
> > > > http://lists.xensource.com/xen-users
> > > >
> > >
> > >
> >
>
>

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users