[Qemu-devel] Re: [PATCH v6 0/5] qed: Add QEMU Enhanced Disk format

[Kevin Wolf]

Am 06.12.2010 17:07, schrieb Stefan Hajnoczi:
> For a changelog against v5, see below.
> 
> 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 base image may be smaller than the image file.
> 
> The file format is extensible so that additional features can be added
> later with graceful compatibility handling.  A specification for the file
> format is included in this patchset.
> 
> 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.
> 
> Signed-off-by: Anthony Liguori <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>

Thanks, reluctantly applied to the block branch. ;-)

Kevin