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Since we're talking snapshots, quick doc-related snapshot questions:

- Are snapshots only supported on qemu/kvm, or do they work with other hypervisors as well? (Does Xen support qcow2 images?)

- Does OpenStack do anything with snapshots other than using them to generate new images? I was a little confused by the existence of the "Snapshots" pane in Diablo Horizon. I originally thought snapshotting was just a qemu/kvm implementation detail about how nova created a new image from a running instance, so I didn't understand why there was a "Snapshots" pane in addition to an "Images" pane.


Take care,

Lorin
--
Lorin Hochstein
Lead Architect - Cloud Services
Nimbis Services, Inc.
www.nimbisservices.com





On Apr 25, 2012, at 1:55 AM, Vishvananda Ishaya wrote:

> ?
> 
> Did you mistype your comment or misread mine?  Raw does NOT work for snapshots. snapshots only work for qcow2. Implementing snapshotting with raw would be possible. Logic just needs to be added to skip the internal snapshot step and just use the entire file when uploading to glance.  This would be pretty darn slow for large images though.
> 
> If you are asking about differencing images in glance that is a different question and one that we haven't addressed. It has a lot of implications and needs changes in both nova and glance to be useful. Logic needs to be added around dependency chains and coalescing. Plus it has implications when trying to migrate and resize instances, so there is a lot to consider.
> 
> As caitlin mentioned, something will be implemented in the volume service anyway, so it might be better to wait and see what happens there.
> 
> Vish
> 
> On Apr 24, 2012, at 4:30 PM, Joshua Harlow wrote:
> 
>> What changes would be needed to make qcow2 files work as snapshots?
>> Some type of image “dependency” management in glance (and failure cases) and the corresponding “dependency” fetching in nova (and failure cases)?
>> Might be something pretty useful to have, instead of forcing raw for snapshots?
>> 
>> On 4/24/12 3:51 PM, "Vishvananda Ishaya" <vishvananda at gmail.com> wrote:
>> 
>> On Apr 17, 2012, at 2:04 AM, William Herry wrote:
>> 
>> > so, what changes should I make if I want use raw in openstack, I didn't find some configure option in nova.conf.sample
>> >
>> > I also try to modify the source code in nova/virt/libvirt/utils.py, and didn't succeed
>> >
>> > I noticed that the type of snapshot is same as the instance's image by default, does this right, and what about the type of model image that uploaded to glance, does it affect the disk type I use?
>> >
>> > Thanks
>> 
>> snapshots will not work with raw images.  To make openstack use raw images, you simply have to set:
>> 
>> use_cow_images=false
>> 
>> you can upload to glance in qcow or raw, it will be decoded to raw when the image is downloaded to the compute host.
>> 
>> Vish
>> 
>> 
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