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On 05/31/2018 04:14 PM, Moore, Curt wrote:

> The challenge is that transferring the Glance image transfer is _glacially slow_
> when using the Glance HTTP API (~30 min for a 50GB Windows image (It’s Windows,
> it’s huge with all of the necessary tools installed)).  If libvirt can instead
> perform an RBD export on the image using the image download functionality, it is
> able to download the same image in ~30 sec.

This seems oddly slow.  I just downloaded a 1.6 GB image from glance in slightly 
under 10 seconds.  That would map to about 5 minutes for a 50GB image.


> We could look at attaching an additional ephemeral disk to the instance and have
> cloudbase-init use it as the pagefile but it appears that if libvirt is using
> rbd for its images_type, _all_ disks must then come from Ceph, there is no way
> at present to allow the VM image to run from Ceph and have an ephemeral disk
> mapped in from node-local storage.  Even still, this would have the effect of
> "wasting" Ceph IOPS for the VM disk itself which could be better used for other
> purposes.
>
> Based on what I have explained about our use case, is there a better/different
> way to accomplish the same goal without using the deprecated image download
> functionality?  If not, can we work to "un-deprecate" the download extension
> point? Should I work to get the code for this RBD download into the upstream
> repository?

Have you considered using compute nodes configured for local storage but then 
use boot-from-volume with cinder and glance both using ceph?  I *think* there's 
an optimization there such that the volume creation is fast.

Assuming the volume creation is indeed fast, in this scenario you could then 
have a local ephemeral/swap disk for your pagefile.  You'd still have your VM 
root disks on ceph though.

Chris