[openstack-dev] More on the topic of DELIMITER, the Quota Management Library proposal

Amrith Kumar amrith at tesora.com
Sat Apr 23 19:53:32 UTC 2016

On Sat, 2016-04-23 at 15:25 -0400, Jay Pipes wrote:
> On 04/23/2016 03:18 PM, Mike Perez wrote:
> > On 14:54 Apr 18, Jay Pipes wrote:
> >> On 04/16/2016 05:51 PM, Amrith Kumar wrote:
> >>>          - update_resource(id or resource, newsize)
> >>
> >> Resizing resources is a bad idea, IMHO. Resources are easier to deal with
> >> when they are considered of immutable size and simple (i.e. not complex or
> >> nested). I think the problem here is in the definition of resource classes
> >> improperly.
> >>
> >> For example, a "cluster" is not a resource. It is a collection of resources
> >> of type node. "Resizing" a cluster is a misnomer, because you aren't
> >> resizing a resource at all. Instead, you are creating or destroying
> >> resources inside the cluster (i.e. joining or leaving cluster nodes).
> >>
> >> BTW, this is also why the "resize instance" API in Nova is such a giant pain
> >> in the ass. It's attempting to "modify" the instance "resource" when the
> >> instance isn't really the resource at all. The VCPU, RAM_MB, DISK_GB, and
> >> PCI devices are the actual resources. The instance is a convenient way to
> >> tie those resources together, and doing a "resize" of the instance behind
> >> the scenes actually performs a *move* operation, which isn't a *change* of
> >> the original resources. Rather, it is a creation of a new set of resources
> >> (of the new amounts) and a deletion of the old set of resources.
> >
> > How about extending a volume? A volume is a resource and can be extended in
> > Cinder today.
> Yep, understood :) I recognize some resource amounts can be modified for 
> some resource classes. How about *shrinking* a volume. Is that supported?

[amrith] It isn't today and every other week or so (most recently this
past Monday in Percona Live) I get a request for this capability :)

Not saying it is easy (I know it is hard) but honestly answering the
question regarding support.

> Best,
> -jay
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