Are there any benefits of using .qcow2 over .img files when trying to create a VM .
I have a smallish debian .iso and have seen at least with .qcow2 that it is slow.
I also saw http://wiki.qemu.org/Features/Qcow3 and these two lines show up there :-
near-raw performance, competitive with QED
Performance analysis has shown that QCOW2 performance is significantly worse than using raw files. Different approaches, including QED's simplified metadata and fully asynchronous implementation, have proven that a modern image format can achieve near-raw performance. Metadata caching and batched updates can also improve performance but require image format changes to be effective in all cases.
Improving performance is the key motivation for a QCOW3 image format.
Can anybody comment. I am guessing that qcow3 is stil up in the air.