[et-mgmt-tools] [PATCH] can not specify the type of driver device

[Daniel P. Berrange]

On Mon, Jul 02, 2007 at 06:29:03PM +0900, Saori Fukuta wrote:
> Hi,
> 
> I opened the new bugzilla:
>   Bugzilla Bug 246441: can not specify the type of driver device
>   URL: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=246441
> 
> And I attached the patch to fix this problem.

There seems to be two different use cases for the driver type, and I'm
not sure which one you are trying to address. The patch seems to be just
giving the user the ability to specify a sub-type for blktap based files.
The code which actually creates the disk image though will always simply
create raw disks - so it doesn't make much sense to specify a custom
driver type there. It explicitly doesn't deal with HVM, even though QEMU
is quite happy dealing with the various disk formats.

Rather than directly specifying a driver type, I think what would be more 
useful is to have an option called

   --disk-format=TYPE

Which accepts TYPE being one of:

   raw
   vmdk
   qcow
   vpc
   cow
   cloop
   dmg

And then 

  - Makes sure the disk image we create is using appropriate file format
  - Automatically choose the best driver type to match the disk type.

One question I wonder is how to best create the actual disk image - with
raw disks its easy - we're either seeking to the end (sparse), or just
writing lots of zeros (non-sparse). The other formats like vmdk, qcow,
etc have some special file structure that needs writing out. We could add
code for doing this in python in virt-install, or we could simply run the
'qemu-img' command to create the file in non-raw case.

The latter would probably be easiest to do, although we'd explicitly need
to add a dependancy on the QEMU rpm, since qemu-img isn't part of the Xen
RPMs, or part of libvirt.

Regards,
Dan.
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