[ Cloud Computing ] Re: why virtualization?

Now I have to chime in ;o) (Dan, see what you got me into !)

 

I did not say elasticity cannot be achieved by virtualization (notice the double negative ;o)); I also didn’t say for elasticity, virtualization is needed ! My point was, they are orthogonal – elasticity can be achieved with or without virtualization. In other words, virtualization is neither a necessity nor a prerequisite for elasticity.

 

Cisco has a product called VFrame which does provisioning and in old days (may be even now) it turns on and off real hardware to get additional capacity. (This is just an example – I am neither advocating for nor against VFrame, in this context) You can have a perfectly good cloud in that way.

 

Having said that, the hypervisors give us couple of things; first - the ability to move VMs around; I am not sure if it also gives us VM expandability as that requires a bit more than just a VM change (applications need to reallocate buffers, move boundaries et al); second - it offers us more granularity and efficient use of hardware. I am not aware of any technology to pickle a running machine and resurrect it somewhere else as easily as the VM motion technologies.

 

Going back to Dan’s original question, for an application - say a hadoop cluster, would virtualization give any advantage ? Same goes with Utpal’s examples of grids and clusters.

 

Let me stop before I get into more trouble ;o)

 

Cheers

<k/>

BTW, the logic which says because Amazon is based on XEN, virtualization is required for elasticity is not logical. Amazon also sells books and that doesn’t mean for elasticity one should sell books ;o) But the second order effects of having an infrastructure which sells lots of books do help (engineers who understand scalability, idle resources when books are not in high demand, a retail mindset and so forth)

 

From: cloud-computing@googlegroups.com [mailto:cloud-computing@googlegroups.com] On Behalf Of Utpal Datta
Sent: Wednesday, December 17, 2008 6:46 PM
To: cloud-computing@googlegroups.com
Subject: [ Cloud Computing ] Re: why virtualization?

 

No one said that elasticity is achievable only thru virtualization. Technologies like Grid, Beowulf was happily being elastic when VMWare was in kindergarten.

 

Shankar claimed that elsticity cannot be achieved by virtualization. I was curious about the validity and reasons behind that statement.

 

The bigger implication is that available compute resources of enterprise ITs which are moving at a breakneck speed towards virualization, cannot be made to behave (just as elastic as EC2) like the external cloud.

 

It is much easier for the enterprise to adopt a internal cloud (no security, data movement issues) and effectively deal with "cloud-burst" as well as much higher utilization, just using virtualization and some smart software which orchestrate the whole thing.

 

Ofcourse the applications which can take advantage of this will have to be smartly re/written by smart people :-)

 

Anyone sees any problem with what is stated above?

On Wed, Dec 17, 2008 at 8:05 PM, Jayadeep <p.jayadeep@gmail.com> wrote:

I guess you can achieve elasticity without virtualization, but
virtualization enables or enhances elasticity by virtue of the
flexibility it brings. But I am not so sure if they are orthogonal,
but they sure are not directly related.

Jayadeep

On Dec 18, 1:00 am, "Utpal Datta" <utpal8...@gmail.com> wrote:
> >> BTW, IMHO, elasticity was never the goal of virtualization not can we
>
> achieve elasticity by virtualization – they are orthogonal
>
> As far as we know, Amazon is based on a Xen infrastructure (i.e.
> virtualization). How are they achieving elasticity and scalability?
>
> --utpal
>

> On 12/17/08, Krishna Sankar (ksankar) <ksan...@cisco.com> wrote:
>
>
>
> >  Dan,
>
> > Good line of thought. Couple of points:
>
> > a)      Power efficiency – I think an 8 core machine (with 7.5 VM
> > processes) would use less power than 8 small machines (say powered by via
> > itx). But if one is using only one VM and one process, then the rest of the
> > power is wasted
>
> > b)      Yes, from an enterprise IT application infrastructure perspective,
> > virtualization s a short term solution with a cloud infrastructure as the
> > long term goal
>
> > c)       Virtualization in some sense is getting more granularity than a
> > hardware box (for better utilization) and that would eventually shift to the
> > infrastructure providers
>
> > d)      BTW, IMHO, elasticity was never the goal of virtualization not can
> > we achieve elasticity by virtualization – they are orthogonal
>
> > e)      Same goes with scale and ad-hocness
>
> > f)       And as you point out, virtualization has serious drawbacks – like
> > multi-core and extra overhead.
>
> > Cheers & happy holidays
>
> > <k/>
>
> > *From:* cloud-computing@googlegroups.com [mailto:
> > cloud-computing@googlegroups.com] *On Behalf Of *Dan Kearns
> > *Sent:* Wednesday, December 17, 2008 9:06 AM
> > *To:* cloud-computing@googlegroups.com
> > *Subject:* [ Cloud Computing ] why virtualization?
>
> > Out of curiosity.... it seems to me that two pretty fundamental tenets of
> > cloud computing are contradictory:
>
> > Virtualization: a mechanism to get better utilization of existing hardware
> > when loads are generally smaller than node capacity, or spiky in the time
> > domain
>
> > Griddiness: (for lack of a better word) the idea that appropriate cloud
> > designs support massive scale, and do it by aggregating many small+cheap
> > failure-prone compute units with smarter software
>
> > If the goals are to have smarter software and maximize utilization (or
> > minimize power consumption for equivalent compute capacity), then why
> > introduce the constant runtime overhead of virtualization instead of, eg
> > using smaller more power-efficient compute-unit designs and making the
> > hardware controllable by software?
>
> > Am I missing something, or is virtualization a tactical answer and
> > therefore a short-term solution, and not a great place to start building
> > management frameworks (for example) on top of?
>
> > -d

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