Open Stack

On 03/16/2017 07:06 PM, Blair Bethwaite wrote:

> Statement: breaks bin packing / have to match flavor dimensions to hardware
> dimensions.
> Comment: neither of these ring true to me given that most operators tend to
> agree that memory is there first constraining resource dimension and it is
> difficult to achieve high CPU utilisation before memory is exhausted. Plus
> virtualisation is inherently about resource sharing and over-provisioning,
> unless you have very detailed knowledge of your workloads a priori (or some
> cycle-stealing/back-filling mechanism) you will always have under-utilisation
> (possibly quite high on average) in some resource dimensions.

I think this would be highly dependent on the workload.  A virtual router is 
going to run out of CPU/network bandwidth far before memory is exhausted.

For similar reasons I'd disagree that virtualization is inherently about 
over-provisioning and suggest that (in some cases at least) it's more about 
flexibility over time.  Our customers generally care about maximizing 
performance and so nothing is over-provisioned...disk, NICs, CPUs, RAM are 
generally all exclusively allocated.

Chris