[ovirt-devel] Unable to import templates

[Nir Soffer]

----- Original Message -----
> From: "Allon Mureinik" <amureini at redhat.com>
> To: "Christopher Pereira" <kripper at imatronix.cl>
> Cc: devel at ovirt.org
> Sent: Thursday, May 28, 2015 3:31:36 PM
> Subject: Re: [ovirt-devel] Unable to import templates
> 
> 
> 
> ----- Original Message -----
> > From: "Christopher Pereira" <kripper at imatronix.cl>
> > To: devel at ovirt.org
> > Sent: Tuesday, May 26, 2015 1:44:16 AM
> > Subject: [ovirt-devel] Unable to import templates
> > 
> > Hi,
> > 
> > A user was unable to import a VM template from a gluster export storage
> > because of various reasons, and since I'm afraid this could hit many
> > users (losing many days waiting for import tasks to...fail) I would like
> > to share the issues and some ideas with you:
> > 
> > 1) Slowness:
> > 
> > FYI, working with sparse files on GlusterFS mounts will be very slow
> > until https://bugzilla.redhat.com/show_bug.cgi?id=1220173 is implemented.
> > Maybe the same applies also to other network file-systems.
> > 
> > 2) Engine Task timeout:
> > 
> > The last times the user tried to import this template (using nightly
> > builds), the task was apparently deleted by Engine because of timeout
> > while the qemu-img process continued running (and consuming resources).
> > I'm not sure, but I believe the tasks are deleted by Engine after 4 or 5
> > days no matter if the qemu-img process is still running (!?).
> > Thus, slow import tasks will never finish.
> > Can someone please confirm?
> > Maybe we can improve something here to support long import tasks.
> Sounds like a bug.
> Could you please report it with all the logs, etc. attached?
> 
> 
> > 
> > 3) Wrong SPM:
> > 
> > If $SRC is on host-1, $DST on host-2 and SPM is host-3, the image will
> > be unnecessarily crossing host-3 and kill the cluster performance.
> > I guess Engine should choose automatically the appropriate SPM host
> > depending on the tasks (host-1 or host-2 in this case).
> > But it seems like oVirt doesn't currently support changing the SPM when
> > there are running tasks, based on the fact that the user gets a warning
> > when trying to do it manually.
> Moving around SPM is WAY too dangerous to do per operation.
> Looking forward, this should be part of the non-SPM architecture, probably
> after 3.6.0.
> 
> > 
> > 4) Convert Optimization:
> > 
> > I see oVirt is running:
> > /usr/bin/qemu-img convert -t none -T none -f raw $SRC -O raw $DST
> > 
> > In this case, $SRC is in raw format and there are no backing chains.
> > 
> > Shouldn't we do a simple 'cp --sparse=always' instead of a 'qemu-img
> > convert' in this case?
> > I guess qemu-img should be doing this optimization for us, but maybe
> > this raw-to-raw conversion use case is just to silly and will not be
> > considered by qemu-img maintainers.
> Definitely worth checking

In general, we prefer to do all image operations using qemu-img. If an
optimization is needed, better do it in qemu-img, improving all users.

But if you send a patch for this and back it up with benchmark results,
proving that this make a significant improvement, I think it should be
easy to get it merged.

Nir