Re: [Xen-users] COW-backed VBDs

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > or use a CoW NFS server (someone in
> > Cambridge developed one but I don't know if the code is floating around).
>
> If you happen accross it I'd love to see it :)

I'll ask around...

> > I'll be working on a CoW filesystem also, later this year.
>
> Great to hear Mark. I'll be looking forward to it. :)

Lots to do yet but if it all works out it should be way kewl.  The only 
trouble is it requires lots of coding to happen first :-)

I doubt I'll ever match the coolness of a UML CoW disk command I remember 
seeing - something like "cow_moo" :-D

Cheers,
Mark

> Cheers,
> John Fairbairn
>
> >> I have asked this question before about COW backed VBD support in Xen.
> >> It
> >> would be really cool if I could share the same root FS between domains,
> >> each having its own COW system.
> >
> > Indeed.
> >
> >> I am typically using file-backed roots. Does Xen (as User-mode linux)
> >> provide utility to create COW disks (linked to a readOnly main disk)
> >> which
> >> can be used as VBDs.
> >
> > You can use LVM2 snapshots or the Device Mapper to create a COW virtual
> > device.  LVM, at least, seems to have some issues with scalability when
> > doing
> > lots of CoW-ing though - make sure dom0 has enough memory.
> >
> > The other way of doing things is CoW at the filesystem, rather than at
> > block
> > level.  E.g. combine NFS and UnionFS or use a CoW NFS server (someone in
> > Cambridge developed one but I don't know if the code is floating around).
> > I'll be working on a CoW filesystem also, later this year.
> >
> > Cheers,
> > Mark
> >
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>
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