On Dec 12, 2013, at 4:05 PM, Jay Dobies wrote:
>> Maybe this is a valid use case?
>>
>> Cloud operator has several core service nodes of differing configuration
>> types.
>>
>> [node1] <-- balanced mix of disk/cpu/ram for general core services
>> [node2] <-- lots of disks for Ceilometer data storage
>> [node3] <-- low-end "appliance like" box for a specialized/custom core
>> service
>> (SIEM box for example)
>>
>> All nodes[1,2,3] are in the same deployment grouping ("core services)". As
>> such,
>> this is a heterogenous deployment grouping. Heterogeneity in this case
>> defined by
>> differing roles and hardware configurations.
>>
>> This is a real use case.
>>
>> How do we handle this?
>
> This is the sort of thing I had been concerned with, but I think this is just
> a variation on Robert's GPU example. Rather than butcher it by paraphrasing,
> I'll just include the relevant part:
>
>
> "The basic stuff we're talking about so far is just about saying each
> role can run on some set of undercloud flavors. If that new bit of kit
> has the same coarse metadata as other kit, Nova can't tell it apart.
> So the way to solve the problem is:
> - a) teach Ironic about the specialness of the node (e.g. a tag 'GPU')
> - b) teach Nova that there is a flavor that maps to the presence of
> that specialness, and
> c) teach Nova that other flavors may not map to that specialness
>
> then in Tuskar whatever Nova configuration is needed to use that GPU
> is a special role ('GPU compute' for instance) and only that role
> would be given that flavor to use. That special config is probably
> being in a host aggregate, with an overcloud flavor that specifies
> that aggregate, which means at the TripleO level we need to put the
> aggregate in the config metadata for that role, and the admin does a
> one-time setup in the Nova Horizon UI to configure their GPU compute
> flavor."
>
Yes, the core services example is a variation on the above. The idea
of _undercloud_ flavor assignment (flavor to role mapping) escaped me
when I read that earlier.
It appears to be very elegant and provides another attribute for Tuskar's
notion of resource classes. So +1 here.
> You mention three specific nodes, but what you're describing is more likely
> three concepts:
> - Balanced Nodes
> - High Disk I/O Nodes
> - Low-End Appliance Nodes
>
> They may have one node in each, but I think your example of three nodes is
> potentially *too* simplified to be considered as proper sample size. I'd
> guess there are more than three in play commonly, in which case the concepts
> breakdown starts to be more appealing.
Correct - definitely more than three, I just wanted to illustrate the use case.
> I think the disk flavor in particular has quite a few use cases, especially
> until SSDs are ubiquitous. I'd want to flag those (in Jay terminology, "the
> disk hotness") as hosting the data-intensive portions, but where I had
> previously been viewing that as manual allocation, it sounds like the
> approach is to properly categorize them for what they are and teach Nova how
> to use them.
>
> Robert - Please correct me if I misread any of what your intention was, I
> don't want to drive people down the wrong path if I'm misinterpretting
> anything.
-k
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