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Virtualization and Private Cloud - Draw a line

Many a times you might get this question, where do I draw a line and say what's virtualization and what's private cloud? While setting up a private cloud lab we had similar question. Though, there is no clear answer, we tried to take out a few characteristics which might help.

There are a lot of definitions of virtualization and cloud as such, let me try to explain it in a simpler way. There are multiple types of virtualization like hardware virtualization, application virtualization, storage virtualization etc. From private cloud perspective we are more interested in Hardware virtualization. Hardware Virtualization technique helps us to simulate multiple hardware boxes out of one single box. It helps creating multiple servers from a single hardware box. The software program which helps achieving this is called as hypervisor. So virtualization helps creating multiple servers from one to improve the utilization of physical boxes in the data center. A physical box which is used for virtualization is referred as Host where as the simulated virtualized boxes within that are referred as Guests. For further discussion let us consider these hardware boxes as resources.

                From simplistic point of view Cloud means unlimited externally located and managed resources available on demand and supports pay as you go model. This definition can be true for public cloud but from private cloud point of view we will have to tweak it a little. Private cloud, as name implies is part of the organization's data center and hence it is referred as private. Practically we cannot apply the characteristic of public cloud saying that it provides unlimited resources. Though, Private cloud has some known limits in terms of resources but it can provide dynamic - on demand resource allocation, management of resources and pay as you go billing/usages.

                Private cloud can be achieved using virtualization but not always necessary. You could create private cloud without virtualization, using a large set of commodity hardware. Private cloud has management, billing and dynamic allocation layer over the virtualized or non-virtualized resource pool. Resources here could virtualize machines, RAM and hard disk allocated to the machines, network bandwidth etc. In nutshell not correct to compare virtualization with private cloud. Virtualization can be used as a building block to achieve private cloud.  Following images should help clarify it better.





Characteristics of Virtualization:

1.       Helps in optimizing resource utilization by emulating multiple resources using one

2.       Manual management of resources like upgrades, patches and maintenance etc.

3.       Manual monitoring and usage

4.       Doesn't provide self service commissioning of resources

5.       It's about infrastructure



Characteristics of Private Cloud

1.       Provides dynamic commissioning and de-commissioning of machines/resources

2.       Automatic and centralized management of available resource pool

3.       Automatic management of resources like upgrades, patches and maintenance etc.

4.       Provides self service commissioning of resources

5.       It's about service delivery

Hope this blog helps in clearing the haze while looking at virtualization and private cloud.


your claim that we can not apply characteristics of public cloud to private cloud about providing unlimited resources, IMHO, seems to be incorrect. Private cloud is afterall a cloud, having all characteristics of any cloud service, except that it resides behind company's firewall and can not be made available to any one outside the firewall.
Virtualization helps realizing private clouds- but again, why can't it be used for public cloud? Thoretically, I would say, you can use any technique, including virtualization, to shape a cloud service - private or public.

Laxman, Thanks for your comment.
In a way it is a valid comment, but if you look at it from the boundary of consumption perspective, in a Private Cloud you know and might hit the limitation of the resources whereas in public cloud it is abstracted from you as a consumer and you assume those are unlimited resources. You could very well say that in private cloud too you have unlimited resources, the idea is not to compare public and private cloud here but to draw a line where private cloud starts and virtualization ends, if at all we used virtualization to setup private cloud.
Secondly, it doesn't mean you cannot use virtualization to build public cloud, did it sound like that?
Again to reiterate the point is not about private and public cloud, it’s all together a different ball game. Look at public cloud service providers, most of the techniques are proprietary and abstracted from the consumer. As pointed out you could setup a cloud with and without the virtualization, but it could be a key technique to setup a cloud.

To me virtualization will be a basic feature or a technique and cloud (private or public) is value added service on top of it. It is like Workflow foundation provides basics of workflows and product like BizTalk offers lot more of packaged features on top of it

I would second atul on that (not entirely with the example though :)), be it hypervisor or some fabric like layer managing your commodity hardware would still constitute to me as virtualization or hardware virtualization as you put it. The additional capabilities provided based on the principles of cloud such as on-demand, self-service , meter-able, being elastic would help bring to fore the distinction between virtualization and cloud

Sidharth, that's exactly the point :-) and I used this example since WF and BizTalk have been around much longer and hence may be easier to understand. It isn't for 100% accuracy, but more to put the point across.

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