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Hi Daniel,

referring to this discussion we had some weeks ago, there is a blueprint 
and spec up for review now, describing the boot device prioritization 
feature you proposed:
https://blueprints.launchpad.net/nova/+spec/boot-order-for-instance
https://review.openstack.org/#/c/133254/

It would be great if you could have a look and add your comments.

Regards, Ondrej

On 10/02/2014 11:56 AM, Daniel P. Berrange wrote:
> When booting from the network there is potentially a choice of multiple
> NICs from which todo PXE.
>
> With KVM you are not restricted to saying disk or network as exclusive
> choices, but rather you can setup arbitrary prioritization of boot order
> across devices, whether disk, nic or PCI assigned device.
>
> So we should really consider this broader problem of boot device
> prioritization not merely a PXE flag. IOW, we should extend the Nova
> boot command so that the --block-device-mapping and --nic args both
> allow for an integer boot priority value to be specified per device.
>
>    bootindex=NNN
>
> And likewise allow it to be set for PCI assigned devices.
>
> Hypervisors that don't support such fine grained ordering, can simply
> ignore anything except the device with bootindex=1.
>
> Regards,
> Daniel