Re: [Qemu-devel] [RFC PATCH 0/2] Sheepdog: distributed storage system for QEMU

[Kevin Wolf]

Am 14.05.2010 11:54, schrieb MORITA Kazutaka:
>>> There is another problem to make the sheepdog driver be a protocol;
>>> how to deal with protocol specific create_options?
>>>
>>> For example, sheepdog supports cloning images as a format driver:
>>>
>>>   $ qemu-img create -f sheepdog dst -b sheepdog:src
>>>
>>> But if the sheepdog driver is a protocol, error will occur.
>>>
>>>   $ qemu-img create sheepdog:dst -b sheepdog:src
>>>   Unknown option 'backing_file'
>>>   qemu-img: Backing file not supported for file format 'raw'
>>>
>>> It is because the raw format doesn't support a backing_file option.
>>> To support the protocol specific create_options, if the format driver
>>> cannot parse some of the arguments, the protocol driver need to parse
>>> them.
>>
>> That's actually a good point. Yes, I think it makes a lot of sense to
>> allow parameters to be passed to the protocol driver.
>>
> 
> Okay. But it seemed to require many changes to the qemu-img parser, so I 
> didn't
> do it in the patchset I sent just now.

Yes, it probably requires a bit more than just five lines. We should
have it in the final version of the patch series, but we seem to agree
there and image creation is separate enough, so we can ignore it for the
discussion of the other parts.

Kevin