[openstack-dev] [nova][ironic] making file injection optional / removing it

Devananda van der Veen devananda.vdv at gmail.com
Mon May 13 16:43:13 UTC 2013


On Mon, May 13, 2013 at 6:44 AM, Jarrod B Johnson <jbjohnso at us.ibm.com>wrote:

<snip>

For cases requiring a deployment environment, file-oriented payload makes
> the most sense, but for virtualization and SAN boot it almost never makes
> sense.  It is less awkward for direct attached storage to do block imaging
> than it is for virtualized and SAN instances to do file-oriented, so block
> oriented I suppose wins if you pick just one.
>

> Fixing up the instance to be bootable.  This would include driver
> injection.
>

I disagree. I do not expect the deployment code to take a generic image,
splat it onto a specific machine, and then know which drivers the machine
needs, where to fetch them from, and how to inject them into the file
system. In a large homogeneous deployment, this will lead to increased
entropy, which will lead to increased failures. It is very desirable to
have a strong guarantee that all instances created from a single image are
identical; IMHO, late-stage driver injection violates this and is therefor
undesirable.

Instead, I suggest that the image(s) should be tailored by the cloud
operator ahead of time to suit their hardware. We are already doing this
with diskimage-builder. See elements/mellanox/ for an example of driver
injection.
  https://github.com/stackforge/diskimage-builder

In a heterogeneous environment, there would need to be a mapping between
cloud images' capabilities and enrolled hardware specifications, such that
only images which match the targeted hardware's characteristics could be
deployed thereon. To a limited extent, this is already possible with Nova
baremetal, and I plan to expand that with Ironic.


Regards,
Devananda
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