Red Hat Bugzilla – Bug 835572
Comparison of storage volume formats
Last modified: 2016-01-26 20:55:08 EST
Please include a comparison of all available storage volume formats:
can you please supply me with some information?
Note that the original report does not include all image formats that qemu-img can handle in RHEL 6. For a hopefuly complete list with a description please see the man page of qemu-img.
In short, we support these native formats:
* raw: Optimal performance, only very basic features (no snapshots etc.)
* qcow2: Full features, at the cost of some performance
* qed: Included only at IBM's request; has less features than qcow2, but can perform a bit better in some specific cases (cache=writethrough). We won't support it as a native format in RHEL 7, please warn against using it.
The other formats are for compatibility with other virtualisation software. They cannot be used for running VMs in RHEL, but only for qemu-img. The idea is that you convert them to raw or qcow2 before using them with KVM.
qed should either not be mentioned at all, or we should warn against using it because it's a dead end and won't be included in future releases. It's description is sub-standard, too (typos, formatting, grammar...)
Also I'm afraid that I didn't describe the distinction between native and compatibility formats precise enough: Native formats can be used to run VMs and also for qemu-img, this is described correctly. Compatibility formats cannot be used to run VMs, but they can be used for all kinds of qemu-img operation, so amongst others you cannot only convert from, but also to them.
Moving back to assigned until comment#7 is addressed.