Comment 9 for bug 1382164

yzveryanskyy, yes, disk reservation feature can also resolve the problem. However, I'd prefer the convert on the fly because it will reduce the disk usage for the ironic conductor node. Considering a ironic conductor was asked to install 100 compute node. Convert to raw image will cause a huge number of disk space. It's basically a trade off of time/space.

Disk reservation is sure to be something helpful!