Open Stack

On Mon, Mar 3, 2014 at 10:43 AM, Sean Dague <sean at dague.net> wrote:
> On 03/03/2014 01:35 PM, Joe Gordon wrote:
>> On Mon, Mar 3, 2014 at 10:01 AM, Zane Bitter <zbitter at redhat.com> wrote:
>>> On 03/03/14 12:32, Joe Gordon wrote:
>>>>>
>>>>>> - if you're reserving resources far before you'll need them, it'll be
>>>>>> cheaper
>>>>
>>>> Why? How does this save a provider money?
>>>
>>>
>>> If an operator has zero information about the level of future demand, they
>>> will have to spend a *lot* of money on excess capacity or risk running out.
>>> If an operator has perfect information about future demand, then they need
>>> spend no money on excess capacity. Everywhere in between, the amount of
>>> extra money they need to spend is a non-increasing function of the amount of
>>> information they have. QED.
>>
>> Sure. if an operator has perfect information about future demand they
>> won't need any excess capacity. But assuming you know some future
>> demand, how do you figure out how much of the future demand you know?
>> But sure I can see this as a potential money saver, but unclear by how
>> much. The Amazon model for this is a reservation is at minimum a year,
>> I am not sure how useful short term reservations would be in
>> determining future demand.
>
> There are other useful things with reservations though. In a private
> context the classic one is running number for close of business. Or
> software team that's working towards a release might want to preallocate
> resources for longer scale runs during a particular week.

Why can't they pre-allocate now?

>
> Reservation can really be about global policy giving some tenants more
> priority in getting resources than others (because you pre-allocate them).
>
> I also know that with a lot of the HPC teams using OpenStack, this is a
> fundamental part of scheduling. Not just the when, but the how long.
> Having systems automatically get reaped after a certain amount of time
> is something they very much want.

Agreed, I think this should either be part of Nova or Heat directly.

>
> So I think the general idea have merrit. I just think we need to make
> sure it integrates well with the rest of OpenStack, which I believe
> means strong coupling to the scheduler.
>
>         -Sean
>
> --
> Sean Dague
> Samsung Research America
> sean at dague.net / sean.dague at samsung.com
> http://dague.net
>
>
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