Re: [Xen-devel] Automation scripts

[Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>]

> I like this suggestion. Instead of having a bunch of templates only, I could 
> also have standby partitions, ready to start immediately. Storage *is* cheap, 
> so the cost is low for this.

I expect it wouldn't be too hard to modify the dm-snap driver to
do this. I think we'd end up with something rather more robust,
as the current snapshot mechanism is very vulnerable to disk
errors and other corruption.

In any event, it snap-dm should probably be modified such that it
shares a kcopyd memory pool among all the active snapshots rather
than allocating 1MB for each.

It's a pity that the snapshot exception table is entirely memory
resident, stored as a hash table. Turning it into an on-disk
tree cached in memory would be better.

All things for the todo list...

Ian
 
> Paul
> 
> On Wednesday 29 September 2004 10:36 pm, Christian Limpach wrote:
> > On Tue, Sep 28, 2004 at 09:21:12AM -0500, Brian Wolfe wrote:
> > > I'm far from having a working automated system right now. I still have
> > > the iSCSI death issues to deal with when combining 2 iSCSI target
> > > devices into a raid-1 array in Domain-0 to be exported to the XenLinux
> > > unprived domain. 8-( NFS roots still periodically "lock up" momentarilly
> > > (~2 to 10 seconds) when using nfs root. SO the solution isn't ready yet.
> > > I do highly reccomend that people use LVM LVs for individual exportable
> > > block devices and to forget about using COWs to "save space". Adding a
> > > 200GB disk is dirt cheap (unless you are talking about scsi) so it's not
> > > worth the savings IMHO to multi-cow a filesystem into 2+ unprived
> > > domains on a single machine. The 1 to 2 GB of saved space just isn't
> > > worth it at $0.10 per GB of disk space. :) Add in the system overhead
> > > and seek times required for COWs after your first FS upgrade and your
> > > return is worse than using separate partitions/LVs in my experience.
> >
> > I think the best use one could get from LVM snapshots is background
> > cloning of filesystems, i.e. you'd use a modified snapshot driver
> > which would slowly create a 1-to-1 copy of the whole partition but
> > allow it to be used immediately, copying being done when the
> > disk/machine is otherwise idle.
> >
> >     christian
> 
> 
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