Re: [Qemu-devel] qemu-iotests 042: zero size image on VMDK

[Stefan Hajnoczi]

On Thu, Apr 18, 2013 at 12:08 PM, Fam Zheng <address@hidden> wrote:
> On Thu, 04/18 09:39, Stefan Hajnoczi wrote:
>> On Thu, Apr 18, 2013 at 03:08:55PM +0800, Fam Zheng wrote:
>> > Currently VMDK block driver fails qemu-iotest case 042 because it
>> > refuses to create block with zero size (silently). Is support for zero
>> > size image desired or should this case be skipped?
>> >
>> >     $ qemu-img create -f vmdk t.vmdk 0
>> >     Formatting 't.vmdk', fmt=vmdk size=0 compat6=off
>> >     qemu-img: t.vmdk: error while creating vmdk: No such file or directory
>>
>> Is there a reason to refuse 0-sized images?  The VMware tools can resize
>> images so it would be possible to grow them later (i.e. the use case is
>> weird but might still be valid).
>>
>> It's also worth checking if VMware tools allow you to create 0-sized
>> image and whether they can operate on them.  If they fail to open or
>> inspect 0-sized images, then QEMU should not create them.
>
> Not possible for VMware tools, either. See the vmware-vdiskmanager behavior 
> here:

There is a possibility that the vmdk.py script is "buggy".  Can you
use only VMware tools to create a 0-byte disk?

If the answer is yes, then there's a bug in vmdk.py and the vmdk block
driver should support creating 0-byte disks.

If no, then we should not allow it either.  This prevents confusion
when users find the qemu-img 0-byte VMDK does not work with VMware or
other tools.

Stefan