Virtualization vs. cloud computing- what's the difference?

Virtualization is deployment of an existing infrastructure to do more services thru a shared mechanism, than just allocating infra on a dedicated model as is done before.

Cloud-computing is a holistic approach of consolidating IT infrastructure across enterprises, to be deployed on a shared-service model. Virtualization could be a sub-set of cloud-computing.

Virtualization is the abstraction for the HW layer so some one can run more than one virtual machine on a single HW machine .

Cloud Computing is a collection of layers formed together to deliver a user friendly IP based computing , virtualization is a layer/module inside cloud computing architecture which will enable the providers to deliver the IaaS "Infrastructure as a Service" on the fly , the most important layer inside cloud and what cloud all about is the SDP "service delivery platform" which will enable the provider to integrate with all layers(virtualization , security , billing , CRM , POS , Portal , Software modules, etc ) together to offer a governed IT services ( IaaS ex. virtual server , SaaS ex. hosted CRM , PaaS ex. app store , XaaS ex. anything can go to cloud ).

some quick compariosns between virtualization and cloud computing
virtualization is technical , cloud computing is business .
virtualization is for IT admins , cloud computing for all .
virtualization is not governed , cloud computing is governed .
etc ....

also there is public cloud "for MSPs" , Private Cloud "for big firms" , Hybrid cloud a collection between the both.

Virtualization presents a view of being able to access multiple applications on different Operating systems at the same time, while abstracting ( virtualizing ) the machine hardware. The main focus of virtualization is to leverage the IT infrastructure (data center machines) in an optimal fashion ( by making use of under utilized machines ) to reduce operational costs. The virtualization softwares like Xen, VMware etc., allow heterogeneous applications and operating systems to be consolidated on the same physical machine, giving each the 'feel' of an independent machine, by virtualizing CPU, storage, network. This architecture helps in optimal use of machine hardware thereby reducing costs.

Cloud Computing deals with the delivery of computing resources ( hardware ) and software ( Software as a Service ) on an 'on-demand / pay per usage' basis. So the idea is to buy such services from Service Providers, rather than hosting the services in your own expensive data centers. Such services are of best use to small - medium sized enterprises who would grow rapidly and scale on demand. The Infrastructure as a Service ( IaaS ) model of cloud computing delivers computing resources on a pay per usage basis, eg. Amazon's EC2.

As far as the relation is concerned, Virtualization helps in realizing Cloud Computing i.e. delivery of computing resources, which in turn hosts the different applications on Virtual machines.

Some more detailed perspectives can be found via these links;

http://www.inclusion.in/index.php?option=com_content&view=article&id=512&Item...

http://ezinearticles.com/?What-Are-the-Differences-Between-Cloud-Computing-an...

http://advice.cio.com/bernard_golden/gartner_agrees_on_virtualization_and_clo...

http://data-centers.in/virtualization-and-cloud-computing/

1. Virtualization is an abstraction of virtual away from physical resources.

2. By virtualizating servers, storage, networking and desktops, it becomes easier to move workloads around and becomes faster to provision new (virtual) resources.

3. As a result, virtualization is one of the key enablers for cloud computing, both private cloud and public cloud.

For a more detailed discussion on the road from virtualization to private cloud computing, watch my keynote presentation from the recent Focus Interactive Summit on Virtualization (especially slide 15) at http://www.focus.com/webcasts/interactive-summit/virtualization-ongoing-revol...

or download the presentation at http://media.focus.com/assets/expert-research/keynote-focus-interactive-summi...

Deploying Virtualization is actually embracing a brilliant technology helping to reduce costs on IT hardware and associated Operational cost.
Deploying a Cloud Model is a IT strategic decision of moving from traditional model of "we will cook what we want to eat " to "lets get it from the restaurant" type of Service oriented efficient/flexible/simple to operate model.
pls note :
- Choosing one approach out of the two is lot easier if its food(:)) and with Enterprise IT it needs heavy thinking(even though it seems going forward cloud is the model)
- To add some perspective "Virtualization" in this example will map to cooking food efficiently with less manual effort,less electricity etc etc..( :) ).
- Bottomline : Cloud or No Cloud it always makes sense cooking your food efficiently. In a Traditional deployment Enterprise will have to ensure they are doing the same and when buying from restaurant the Restaurant guys should be doing it.

And when talking SaaS think of it as a type of dish from the Restaurant's menu. The same restaurant(cloud provider) can also provide Daas,PaaS,IaaS as well. In simple terms SaaS is one of the offering from a cloud.

bit more detailed on http://chalkcloud.com/?p=94

Virtualization is only one of the fundamental elements of Cloud computing. Cloud computing is a much broader technology. Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources, for e.g., networks, servers, storage, applications and services, that can be rapidly provisioned and released with minimal management effort or service provider interaction. Cloud model is composed of five essential characteristics, viz., on-demand self-service; broad network access; resource pooling; rapid elasticity; and measured service. A cloud infrastructure is the collection of hardware and software that enables the five essential characteristics of cloud computing.

http://www.myrealdata.com/cloud-computing.html

Virtualization and cloud tend to be one in the same based of the same reasoning to allocate resources as needed. As others have said the cloud is basically far more dynamic then a virtual environment where the resources used are generally static. That's the basic explanation but there is alot more depth that others have already elaborated on.

Thanks for starting this discussion. There are lots of definitions and perspectives on the technology shift in the marketplace I think. (Great for sales professionals, true? e.g. "Y2K".) From my perspective "Cloud Computing" is a bit "cloudy". I believe this is primarily due to "legacy" vendors claiming cloud compatibility by adding in a layer of technology (such as virtualization, I think but will defer to the experts) to enable the customer to access old applications via the Internet. That said, one of the main characteristics of a "Cloud" application is a single, "versionless" code set. Here's my example - What version of Focus.com are you running right now? Thx, GAP

We have an explanation and video on server virtualization here. It might help you understand virtualization a bit better

http://www.ers.ie/Virtualization.html