Description of problem: When cloning vm from snapshot, if the snapshot contains sprase 'raw' disk in file domains and the disk allocation ratio is very low, the cloning process would waste a lot of time processing zeros. If we could use cow format in file domains, the cloning process could be much faster, since zeros are skipped. AFAIK, oVirt rest api have capability to add 'cow' format disk in file domains. But in webadmin portal, we can only use 'raw' disk format for file storage domains. So why not support it ?
Marking as 3.6.0 for consideration when planning the new version.
Processing zeros should not take a lot of time. Either less or as much time as processing data. Once you have a snapshot you already have COW. Perhaps I'm missing the issue here? I'm not sure I see the justification for this feature - please elaborate (and provide performance comparison). CLOSING for the time being.