[sheepdog] [PATCH v2] collie: don't roundup vdi size

[Joseph Glanville]

This is usually handled by doing a full sector read and then only
returning the portion of the buffer requested.
Same goes for writes, read-modify-write is used for sub-sector writes
in these sorts of systems.

In terms of Openstack Glance you just need to implement a custom
iterator for reading the VDI that takes care of doing the buffering.
Sheepdog doesn't need to be modified to do this, just buffer the data
in Python. :)

Are you writing the Glance store driver atm? I would like to help if
you have it up somewhere.
I also have a patch that implements clone for the Sheepdog driver in
Cinder, I will submit for Havana shortly.

On Tue, May 21, 2013 at 5:33 AM, Liu Yuan <namei.unix at gmail.com> wrote:
> On 05/21/2013 08:26 PM, MORITA Kazutaka wrote:
>> Nack, the data length must be sector aligned when we use direct I/O.
>> Can't we modify Glance sheepdog driver so that we don't need these
>> changes?
>
> Just test create an image with size '3' and  write 'XXX' to it. When it
> reads the content, we return 512 bytes. so fail the test. But if user
> requests to read 3 bytes, we should return 3 bytes, no more no less if
> we later support an object store like swift and s3, no?
>
> Thanks,
> Yuan
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