Default use of caching on raw volumes

[Jamie Strandboge]

On Thu, 2010-09-02 at 08:15 -0500, Serge E. Hallyn wrote:
> Quoting Alex Muntada (alexm at alexm.org):
> > + Serge E. Hallyn <serge.hallyn at canonical.com> wrote:
> > 
> > > From what I see online it definately seems to make a huge difference.
> > > For Lucid and Maverick I think the best we can do at this point is to
> > > tell the user about it.  For Natty, well the best option is to have you
> > > work with upstream to change the default there.  Sounds like you've got
> > > a posse forming to back you up  :)
> > 
> > Just want to point out that there's a bug about this on LP:
> > https://bugs.launchpad.net/ubuntu/+source/virt-manager/+bug/568445
> 
> Hm, I see, and Anthony's comment #6 makes a lot of sense to me.
> Like he says, I only use virt-manager for casual use.  For real
> tests, well I tend to use kvm cmdline, but on remote servers
> lately I use libvirt directly so that I can do things like create
> base.xml, then
> 	for i in `seq 1 20`; do
> 		cp base.xml vm$i.xml
> 		sed -i 'whatever' vm$i.xml
> 		virsh define vm$i.xml
> 	done
> 
> So I guess before we consider carrying a patch just in ubuntu,
> we should answer the question - do we expect users who are trying
> out kvm just once to use virt-manager or testdrive?

Anthony's observation about virt-manager may be valid, but I sure know a
lot of people who use it every day as a part of their daily workflow (me
not included -- I use virsh/libvirt exclusively (surprise)).

I like Serge's idea of testing and if there is a positive improvement,
make the change in libvirt itself so all consumers (like eucalyptus,
openstack, straight virsh users, etc) can benefit. If that doesn't fit
virt-manager use cases, update it to use a different sensible default.

-- 
Jamie Strandboge             | http://www.canonical.com
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