Re: [Xen-users] Support for file-based COW, present and future

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

On Mon, Jul 12, 2010 at 2:11 PM, Grant McWilliams
<grantmasterflash@xxxxxxxxx> wrote:
> On Sun, Jul 11, 2010 at 8:28 PM, Garrett Robinson
> <Garrett.Robinson@xxxxxxxxxxx> wrote:
>>
>> I am currently working on a project that would be well-served by a
>> file-based COW filesystem such as is theoretically offered by QCOW,

>> What I'm really wondering is this: Has anybody has
>> success with implementing COW filesystems for their Xen guests using any
>> system, but in particular a file-based one? And does anybody know the
>> present status or future of COW/QCOW implementation in Xen?

> I fought with qcow and qcow2 with Xen for way too long. It seemed that no
> matter what version of Xen and the Linux kernel I was using there was always
> a bug that kept qcow from working. I eventually gave up. Rumor has it that
> Xen4 has working cow if you can get blktap2 to function.

If you want to use copy-on-write file backingstore, I'd actually
suggest using Xen 4. And even then it might be better to use vhd
instead of qcow.

http://wiki.xensource.com/xenwiki/blktap2
http://lxr.xensource.com/lxr/source/tools/blktap2/README

Personally, I gave up trying to use qcow a long time ago, settling
instead for storage-based COW functionality using zfs-fuse.

-- 
Fajar

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