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

[Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>]

On Fri, Dec 17, 2010 at 02:08:16PM +0100, Kevin Wolf wrote:
> 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 <aliguori@us.ibm.com>
> > Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> 
> Thanks, reluctantly applied to the block branch. ;-)

Thank you Kevin!

Stefan