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From David Nalley <da...@gnsa.us>
Subject Re: [DISCUSS] Scaling up CPU and RAM for running VMs
Date Sat, 15 Dec 2012 22:25:53 GMT
On Sat, Dec 15, 2012 at 12:43 PM, Koushik Das <koushik.das@citrix.com> wrote:
> Currently CS supports changing CPU and RAM for stopped VM. This is achieved by changing
compute offering of the VM (with new CPU and RAM values) and then starting it. I am planning
to extend the same for running VM as well. Initially planning to do it for Vmware where CPU
and RAM can be dynamically increased. Support of other HVs can also be added if they support
increasing CPU/RAM.
>
> Assuming that in the updated compute offering only CPU and RAM has changed, the deployment
planner can either select the same host in which case the values are dynamically scaled up
OR a different one in which case the operation fails. In future if there is support for live
migration (provided HV supports it) then another option in the latter case could be to migrate
the VM first and then scale it up.
>
> I will start working on the FS and share it out sometime next week.

Thanks for starting this conversation early in the process, Koushik.

I'd want to make just 'how much' resources can be scaled up a
configuration option. Is 2x reasonable? probably, is 50x reasonable,
probably not.
Or actually - thinking about this - perhaps this becomes part of the
service offering. You can start at 2cores/4gb but have a place to
scale up to without restart, but you know from the outset exactly how
far that is. Actually - since you can't scale it back down, that makes
even more sense to me. (I know you can't scale back down in KVM, not
so sure about VMware) I am worried about the effect of this on usage
statistics, but still sounds very useful.

Maybe you solve the allocation problem by actually allocating for the
max allocatable - of course if that goes into usage metrics, and then
on to billing perhaps it isn't as attractive.

--David

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