[openstack-dev] [TripleO] [Ironic] Roadmap towards heterogenous hardware support

Tomas Sedovic tsedovic at redhat.com
Thu Jan 30 15:14:28 UTC 2014

On 30/01/14 15:53, Matt Wagner wrote:
> On 1/30/14, 5:26 AM, Tomas Sedovic wrote:
>> Hi all,
>> I've seen some confusion regarding the homogenous hardware support as
>> the first step for the tripleo UI. I think it's time to make sure we're
>> all on the same page.
>> Here's what I think is not controversial:
>> 1. Build the UI and everything underneath to work with homogenous
>> hardware in the Icehouse timeframe
>> 2. Figure out how to support heterogenous hardware and do that (may or
>> may not happen within Icehouse)
>> The first option implies having a single nova flavour that will match
>> all the boxes we want to work with. It may or may not be surfaced in the
>> UI (I think that depends on our undercloud installation story).
>> Now, someone (I don't honestly know who or when) proposed a slight step
>> up from point #1 that would allow people to try the UI even if their
>> hardware varies slightly:
>> 1.1 Treat similar hardware configuration as equal
>> The way I understand it is this: we use a scheduler filter that wouldn't
>> do a strict match on the hardware in Ironic. E.g. if our baremetal
>> flavour said 16GB ram and 1TB disk, it would also match a node with 24GB
>> ram or 1.5TB disk.
>> The UI would still assume homogenous hardware and treat it as such. It's
>> just that we would allow for small differences.
>> This *isn't* proposing we match ARM to x64 or offer a box with 24GB RAM
>> when the flavour says 32. We would treat the flavour as a lowest common
>> denominator.
> Does Nova already handle this? Or is it built on exact matches?

It's doing an exact match as far as I know. This would likely involve 
writing a custom filter for nova scheduler and updating nova.conf 

> I guess my question is -- what is the benefit of doing this? Is it just
> so people can play around with it? Or is there a lasting benefit
> long-term? I can see one -- match to the closest, but be willing to give
> me more than I asked for if that's all that's available. Is there any
> downside to this being permanent behavior?

Absolutely not a long term thing. This is just to let people play around 
with the MVP until we have the proper support for heterogenous hardware in.

It's just an idea that would increase the usefulness of the first 
version and should be trivial to implement and take out.

If neither is the case or if we will in fact manage to have a proper 
heterogenous hardware support early (in Icehouse), it doesn't make any 
sense to do this.

> I think the lowest-common-denominator match will be familiar to
> sysadmins, too. Want to do RAID striping across a 500GB and a 750GB
> disk? You'll get a striped 500GB volume.
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