On Mon, Sep 27, 2010 at 11:13 AM, Avi Kivity <a...@redhat.com> wrote: > On 09/23/2010 05:41 PM, Stefan Hajnoczi wrote: >> >> QEMU Enhanced Disk format is a disk image format that forgoes features >> found in qcow2 in favor of better levels of performance and data >> integrity. Due to its simpler on-disk layout, it is possible to safely >> perform metadata updates more efficiently. >> >> Installations, suspend-to-disk, and other allocation-heavy I/O workloads >> will see increased performance due to fewer I/Os and syncs. Workloads >> that do not cause new clusters to be allocated will perform similar to >> raw images due to in-memory metadata caching. >> >> The format supports sparse disk images. It does not rely on the host >> filesystem holes feature, making it a good choice for sparse disk images >> that need to be transferred over channels where holes are not supported. >> >> Backing files are supported so only deltas against a base image can be >> stored. >> >> The file format is extensible so that additional features can be added >> later with graceful compatibility handling. >> >> Internal snapshots are not supported. This eliminates the need for >> additional metadata to track copy-on-write clusters. >> >> Compression and encryption are not supported. They add complexity and can >> be >> implemented at other layers in the stack (i.e. inside the guest or on the >> host). Encryption has been identified as a potential future extension and >> the >> file format allows for this. >> > > IMO the file format should be part of this patchset. Wikis are nice but > they aren't a good place for authoritative documentation.
Good idea. Will add the specification in v2. Stefan
