Open Stack

On 03/06/2013 04:12 PM, Mark Lehrer wrote:
> 
>>> The change I made that helped the most was to disable NBD.  You have
>>
>> Was that to disable injection at startup?
> 
> No, NBD is just slow and unreliable for some reason.  Disabling it made
> my users happy.  I haven't had time to find out why NBD is so horrible.
> 
> Eventually I would like to see /var/lib/glance/images and
> /var/lib/nova/instances/_base be on the same BTRFS file system and use
> reflink copies.

Good call on that.
`cp --reflink=auto` will do a reflink if possible or a normal copy otherwise.
There are two related changes for grizzly.

The first was with use_cow_images=True and force_raw_images=False,
there is actually no transformation done to the image in _base
and so one might be able to even `cp -l` in this case.
That's a bit of a layering violation though, but it might
be possible to handle within nova.

The second is support for direct copy from glance to nova:
https://github.com/openstack/nova/commit/20fca1a2
That isn't ideal at present as it uses shutil.copy()
but it's probably easy to update to calling `cp --reflink=auto`

thanks,
Pádraig.