I've just loaded a full disk qcow2 image from [1] to nova. I've noticed that the disk is not "resized up" as it is if a partition image is loaded. (Note related bug 833265)
Ie, given these 2 images, both running as 'm1.small' in this cloud:
ami-00000067 private smoser-bucket/oneiric-server-cloudimg-amd64-disk1.qcow2.manifest.xml
ami-00000066 public smoser-ubuntu-images-testing/ubuntu-oneiric-daily-amd64-server-20110829.img.manifest.xml
Where:
$ qemu-img info oneiric-server-cloudimg-amd64-disk1.qcow2
image: oneiric-server-cloudimg-amd64-disk1.qcow2
file format: qcow2
virtual size: 2.0G (2147483648 bytes)
disk size: 194M
cluster_size: 65536
An m1.small instance launched from the qcow2 disk gets:
$ df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 2.0G 575M 1.3G 31% /
$ grep . /proc/partitions
major minor #blocks name
253 0 2097152 vda
253 1 2088450 vda1
253 16 20971520 vdb
But a m1.small instance launched from the partition image (ami-00000066) gets:
$ df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/vda 9.9G 576M 8.8G 7% /
$ grep . /proc/partitions
major minor #blocks name
253 0 10485760 vda
253 16 20971520 vdb
Note, I'm not expecting nova to rewrite the partition table and then attempt to resize the partition filesystems inside. I explicitly do not want that. I am asking that nova simply grow the disk, extending it with zeros.
The Ubuntu images have code that will rewrite the partition table on first boot if the disk is larger than the first partition [2], so all that is needed is to grow the disk.
[1] https://cloud-images.ubuntu.com/server/oneiric/current/
[2] http://ubuntu-smoser.blogspot.com/2011/03/todo-start-1104-instance-with-larger.html
Scott: thanks for the info there. I thought it was using truncate to expand the image, but it may not be doing so, especially in the case of a qcow2 disk.