On Fri, Mar 06, 2015 at 03:48:40PM -0500, Mo Morsi wrote:
On 03/06/2015 12:00 PM, Kashyap Chamarthy wrote:
>On Thu, Mar 05, 2015 at 11:48:08AM -0700, Mike Ruckman wrote:
>>Fellow cloudies,
>>
>>The recent builds of our images are v3 qcow2 (also known as qcow3).
>>This presents a problem for our testing, since the openstack instances
>>we have access to don't support v3, only v2. The only difference
>>between v2 and v3 are some performance enhancements -
>Right, just some details on the said performance enhancements in QCOW2
>v3 format, from my notes (about a year old) from an earlier discussion
>w/ some QEMU developers, the two new features in v3 of QCOW2:
>
> (1) lazy_refcounts -- A performance optimization interesting only when
> using 'cache=writethrough'. Useful when guest crashes or powers off.
> (2) Zero clusters -- Useful for (disk) image streaming over slow
> networks.
>
>
Perhaps of interest:
http://talk.manageiq.org/t/qcow-image-format-versions-2-3-analysis/491
Yep, it is interesting.
Thanks for the pointer, Mo.
--
/kashyap