Large uncompressed image size makes uvtool unwieldy on small systems

[Mike Pontillo]

I noticed that the size of the qcow2 images uvtool places on disk are much larger than those I am using with another test tool (which syncs the qcow2 cloud images from rsync://cloud-images.ubuntu.com/cloud-images/$DISTRO/current/ -- and gets the same images, I presume):

$ du -sh ~/.cloud-images/trusty/trusty-server-cloudimg-amd64-disk1.img
249M /home/mpontillo/.cloud-images/trusty/trusty-server-cloudimg-amd64-disk1.img

$ scripts/uvt-show-images
831M /var/lib/uvtool/libvirt/images/x-uvt-b64-Y29tLnVidW50dS5jbG91ZDpzZXJ2ZXI6MTQuMDQ6YW1kNjQgMjAxNjEyMTM= com.ubuntu.cloud:server:14.04:amd64_20161213

After speaking with the uvtool developers, I understand that uvtool seems to convert the images to uncompressed qcow2.

Uncompressing the images might be the preferred strategy for some users, especially on CPU-bound servers with large amounts of storage, but I prefer the faster sync times and lower disk usage of compressed images (as-is).

Others using uvtool on smaller, portable systems (such as a laptop or demo NUC) might also prefer the smaller image size.

There is some concern that using the compressed images is slower and more CPU intensive. However, the compressed images are plenty fast for my purposes (testing MAAS on a laptop).

There should be an option to allow using the images as-is, rather than requiring the decompression step.