Open Stack

On 6 August 2014 18:54, Jay Pipes <jaypipes at gmail.com> wrote:
> So, Liyi Meng has an interesting patch up for Nova:
>
> https://review.openstack.org/#/c/104876
>
> 1) We should just deprecate both the options, with a note in the option help
> text that these options are not used when volume size is not 0, and that the
> interval is calculated based on volume size

This feels bad.

> 2) We should deprecate the CONF.block_device_allocate_retries_interval
> option only, and keep the CONF.block_device_allocate_retries configuration
> option as-is, changing the help text to read something like "Max number of
> retries. We calculate the interval of the retry based on the size of the
> volume."

What about a slight modification to (2)...

3) CONF.block_device_allocate_retries_interval=-1 means calculate
using volume size, and we make it the default, so people can still
override it if they want to. But we also deprecate the option with a
view of removing it during Kilo? Move
CONF.block_device_allocate_retries as max retries.

> I bring this up on the mailing list because I think Liyi's patch offers an
> interesting future direction to the way that we think about our retry
> approach in Nova. Instead of having hard-coded or configurable interval
> times, I think Liyi's approach of calculating the interval length based on
> some input values is a good direction to take.

Seems like the right direction.

But I do worry that its quite dependent on the storage backend.
Sometimes the volume create is almost "free" regardless of the volume
size (with certain types of CoW). So maybe we end up needing some kind
of scaling factor on the weights. I kinda hope I am over thinking
that, and in reality it all works fine. I suspect that is the case.

Thanks,
John