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From Marcus <>
Subject Re: [RFC] adding volume provisioning method option
Date Sat, 01 Feb 2014 06:29:34 GMT
I don't think there needs to be a lot of engineering around this, we
can probably just turn on preallocation=metadata by default.

If there are any other options/features you want to add (such as
preallocation=full), they can simply be turned on via
and/or global/hypervisor/cluster config settings.

If you want control for per-disk settings, you'd probably have to add
it to disk offerings. I don't really think that's necessary, but some
may find it useful.

Note that templates are copied in place as-is for qcow2, so however
the original template was created will remain intact. However, it's
just a backing file so the new qcow2 that stores changes will need to
have settings as well.

On Fri, Jan 31, 2014 at 11:01 PM, Marcus <> wrote:
> I don't think preallocation=metadata is required for sparse qcow2.
> Just if you want it to NOT be sparse for metadata.
> I also remember hearing that either recent qemu-img has a decent
> preallocation by default now, or that performance has improved such
> that it doesn't matter. Will need to do some reading to remember, but
> I think I remember hearing it's not a big deal nowadays.
> On Fri, Jan 31, 2014 at 10:04 PM, Yoshikazu Nojima <> wrote:
>> Hello Nux,
>> Thank you for your comment. I will prepare feature specification.
>> Regards,
>> 2014-01-31 Nux! <>:
>>> On 31.01.2014 20:24, Yoshikazu Nojima wrote:
>>>> Afternoon All,
>>>> Is there anyone working on adding volume provisioning method option?
>>>> As you know, thin provisioning of a volume save consumption of a
>>>> storage, and fat provisioning improves IOPS performance.
>>>> Especially, Qcow2 can save storage consumption and achive relatively
>>>> better performance than default by provisioning a volume with an
>>>> option "preallocation=metadata", which makes an image file a sparse
>>>> file.
>>>> Any thoughts about this?
>>>> If it is ok, I will write a feature specification on confluence and
>>>> start implementation.
>>>> Regards,
>>>> Noji
>>>> Yoshikazu Nojima <>
>>> Hello,
>>> I thought preallocation=metadata is common practice since years. Now I find
>>> out ACS doesn't actually use it?
>>> If so, this is really _bad_ and needs to be fixed ASAP...
>>> Thanks Noji
>>> --
>>> Sent from the Delta quadrant using Borg technology!
>>> Nux!

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