Open Stack

Hi Robert,

I use a combination of host aggregates, instance extraspecs, and the
scheduler filters
AggregateInstanceExtraSpecsFilter,AggregateCoreFilter,AggregateRamFilter
to achieve this in a predictable manner.

The AggregateCoreFilter and AggregateRamFilter allow you to set
ram_allocation_ratio and cpu_allocation_ratio in the aggregate
metadata overriding the value in nova.conf on the scheduler node (but
falling back to that if undefined).  I also set an other descriptive
key like db_host=true or something
 to abstract the specific values from the goal I'm trying to achieve.

By creating special instance types with extraspecs that match this
descriptive key, instances of that type will only run on aggregates
that have matching metadata key value pairs.
  This is the work of the AggregateInstanceExtraSpecsFilter.

I've run this for about a year using Grizzly (which took some filter
back porting) and Havana and have been pretty happy with it .  I
though I wrote something up about how to implement it but can't seem
to find a link to that, let me know if you want a step by step & I'll
either try and find it or find somewhere to write up a new version.

-Jon

On Thu, Jul 10, 2014 at 8:38 AM, Robert van Leeuwen
<Robert.vanLeeuwen at spilgames.com> wrote:
> Hi,
>
> Just wondering if this is possible:
> We have some hypervisors which are dedicated for running database instances.
> I'd like to use a ram_allocation_ratio of 1.0 for these but 1.5 for the other hypervisors.
>
> Is this something that can be set per machine or is this global?
> The documentation says:
> "This filter can be configured to allow a fixed amount of RAM overcommitment by using the ram_allocation_ratio configuration option in nova.conf."
> But is this setting only used on the scheduler machine or is this a per hypervisor setting?
>
> Thx,
> Robert van Leeuwen
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