[Libvir] [Libvirt] Proposal to add 3 functions for VBDs (Virtual Block Devices)

Daniel P. Berrange berrange at redhat.com
Thu Aug 24 16:58:02 UTC 2006

On Thu, Aug 24, 2006 at 12:51:58PM -0400, Daniel Veillard wrote:
> On Thu, Aug 24, 2006 at 05:54:21PM +0200, Philippe Berthault wrote:
> > I think that, instead of designate the backend domain by its id, it 
> > would be better to designate it by its name.
> > This is because the id isn't fix, excepted for the domain-0.
>   Right, providing a flexible and generic enough naming scheme is probably
> the best, using strings is definitely better IMHO. Usually devices will
> be associated to existing devices or files, which will be referenced by
> names. If those resources doesn't exist as such or can't be named, it's 
> better to still build a naming scheme around the mechanism, for example:
>     'xen:vbd:0:1234' or 'xen:vif:2:0123' 
> and using those names separates the API from the specifics, while allowing
> some flexibility.

This is just exposing xen specific attributes via the backdoor, rather 
than via an explicit API. The result is same - applications will become
more dependant on particular hypervisor impementation details.

If we're going to expose block info & allow attach / detach, we should
follow the data format already exposed for block devices in the XML:

  - device name   - eg  hda, xvda1, xvda1, etc
  - backing store - path to a file 
  - type - phys / file
  - readonly - boolean
  - type - floppy, cdrom, disk

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