[occi-wg] Horizontal & vertical scalability in the cloud

Sam Johnston samj at samj.net
Sun Oct 25 21:56:39 CDT 2009


I think you've touched on an interesting point there which ties in to the
"need" for a universal compute unit. More specifically, "cores" aren't a
standard unit of measurement (at least without arch and speed), and in any
cloud that's not brand new you're going to end up with a mix of core speeds
depending on what presented the best value at
build/replacement/expansion/failure time.

If you have a mix of core speeds at a given tier without sufficiently
intelligent load balancing (e.g. response time based) then you'll end up
with some cores being underutilised and/or finishing jobs faster, and others
being unable to keep up. If you're applying the buffalo theory (e.g. round
robin) then you're only as fast as your slowest machines.

Simple fix is to ensure that "clones" or "shadows" of a given compute
resource are all identical, but it's worth keeping in mind nonetheless.


On Mon, Oct 26, 2009 at 4:22 AM, Gary Mazz <garymazzaferro at gmail.com> wrote:

> 'horizontal' and 'vertical' dials is a good idea to define.
> @Andy,  I'm a little confused on the definition of horizontal
> saleability. Aren't the cpus in a single operating image a vertical
> workload capacity much like the amount RAM . If the number of images
> scaled, that would be horizontal because there is no necessity for the
> images to be the same workload set.
> I would prefer to see the dials tied to a standard "meter of work". An
> efficiency metric instead of an "equivalence" of cpu count and ghz and
> RAM amount. Juggling these dials may not be as effectual as the consumer
> perceives when a provider decide to throttle back performance and starts
> dropping workload requests. Without a referenced  "effective workload"
> metric, it may be tough to ascertain if the dials effect anything, other
> than the charge to the customer.
> gary
> Randy Bias wrote:
> >
> > On Oct 25, 2009, at 5:38 PM, Sam Johnston wrote:
> >> A better approach to scalability is to have a single object which you
> >> can both adjust the resources of (vertical scalability) and adjust
> >> the number of instances of (horizontal scalability). That is, you
> >> start a single instance with 1 core and 1Gb, then while it's running
> >> you crank it up to 2 cores and 2Gb. Eventually you max out at say 8
> >> cores and 16Gb so you need to go horizontal at some point. Rather
> >> than create new unlinked instances the idea is that you would simply
> >> adjust the
> >
> > I agree.  This is the future.  Dials for 'horizontal' and for
> > 'vertical', probably attached to a given tier of an application.
> >
> > Just as an FYI, I think 'scale-up' VMs are going to be more and more
> > common.  We'll see VMs with a *lot* more RAM and cores very soon now.
> >  Most of the modern OSes handle hotplug of CPU/RAM pretty well.
> >
> >
> > Best,
> >
> >
> > --Randy
> >
> >
> > Randy Bias, Founder & Cloud Strategist, Cloudscaling
> > +1 (415) 939-8507 [m], randyb at cloudscaling.com
> > <mailto:randyb at neotactics.com>
> > BLOG: http://cloudscaling.com/blog
> >
> >
> >
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