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On 03/05/2013 02:07 PM, Balamurugan V G wrote:
> Thanks for the responses and the link to pixelbeat. Its very helpful.
> 
> Start with QCOW, even before image is uploaded to Glance, dit help since the image size camedown from 20Gb to 8+Gb. I even set the the force_raw_images=False, and use_cow_images=True in nova.conf and restarted nova services. I still see that the image is copied to _base and then copied again to instances folder. This is probably expected and is the caching feature. But under _base I see two files one with the underscore suffix and one without. Does it mean that each time I launch an instance with a diferent flavour(say disk set to 30Gb), another copy will be created in _base?
> 
> root at openstack-kvm1:/var/lib/nova/instances# ls -l _base/ | grep 2b4a8e97317619077645de369a8f9fd63acd1f05
> -rw-rw-r-- 1 nova         nova  8691056640 Mar  5 19:23 2b4a8e97317619077645de369a8f9fd63acd1f05
> -rw-rw-r-- 1 libvirt-qemu kvm   8691056640 Mar  5 19:23 2b4a8e97317619077645de369a8f9fd63acd1f05_20

These files in base are only update once per source image / size combination.
I.E. if you have 100 instances booted from a 20G flavor,
you'll only have those 2 files cached on the first boot.
Note there is a blueprint in place for precaching those too:
https://blueprints.launchpad.net/nova/+spec/nova-image-cache-management-2

thanks,
Pádraig.

p.s. those _20 files will not be there for grizzly
as the caching was adjusted there.