在很多资料或文献中很难找到虚拟化和云计算的区别，甚至连云计算是什么都颇有争议。在网上找到几片论述这一问题的文章，摘录于下。
1. Cloud is an operations model, not technology: http://news.cnet.com/8301-19413_3-10249486-240.html
2. Difference Between Virtualization and Cloud Computing: http://data-centers.in/virtualization-and-cloud-computing/
3. The Difference Between Virtualization and Cloud Computing: http://www.erpsoftwareblog.com/2010/08/the-difference-between-virtualization-and-cloud-computing/
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1. Cloud is an operations model, not technology: http://news.cnet.com/8301-19413_3-10249486-240.html
One of the most common questions I get from those exploring cloud computing for the first time is "what is the difference between cloud computing and virtualization?" It is an excellent question, as most IT departments are currently exploring the ways in which virtualization enables
automation and provisioning agility. Given the fact that cloud is often touted for providing similar benefits, it can be confusing to understand why the two terms aren't equivalent.
My response to that question requires a bit of explanation, so let's step through the differences between the two concepts.
Virtualization is a technology.
(Credit:CNET/James Urquhart)
When you run software in a virtual machine, the bits that represent the program's instructions run through a layer of software that "pretends" to be a dedicated server infrastructure, the hypervisor. The hypervisor is the heart and soul of server virtualization,
and is the enabler of the consolidation and agility values that virtualization brings to the data center.
It is because of the hypervisor that virtualization is the true disruptive technology that enables cloud computing on a massive scale. Hypervisors allow servers to be multi-tenant without rewriting applications to be multi-tenant. Hypervisors allow operating
systems and applications to install to a consistent hardware profile, even though they end up running on a variety of actual physical system implementations. Hypervisors also allow servers to be manipulated by software APIs, which greatly simplifies the act
of automating IT operations.
Cloud computing is an operations model, not a technology.
When you run an application in a public or private cloud, there is no "cloud layer" that your software must pass through in order to leverage the physical infrastructure available to it. In the vast majority of cases, there is probably some virtualization involved,
but the existence of hypervisors clearly does not make your data center resources into a cloud. Nor is the fact that Amazon
EC2 uses Xen hypervisors the reason that they are a cloud.
What makes a cloud a cloud is the fact that the physical resources involved are operated to deliver abstracted IT resources on-demand, at scale, and (almost always) in a multi-tenant environment. It is how you use the technologies involved. For the most part,
cloud computing uses the same management tools, operating systems, middleware, databases, server platforms, network cabling, storage arrays, and so on, that we have come to know and love over the last several decades.
Specific technologies, of course, gain significant importance in a cloud computing environment, such as policy-driven automation, metering systems, and self-service provisioning portals. However, all of these technologies--with the possible exception of the
self-service portal--existed before cloud computing became a much hyped paradigm.
There is no doubt cloud borrows much from long established technologies. It is also true that cloud has borrowed from many long standing operations models, such as mainframe service bureaus. However, the combination of on-demand, at scale, in a multi-tenant
infrastructure is relatively unique for the post client-server era, and is the reason why cloud computing is disruptive, rather than just another operations fad.
In the process of Cloud Computing easily scalable and mostly virtualized data resources are provided to the users over the internet. Using Cloud computing colocation provider or Data Centers providers offer managed IT services via a hosted software as a service
model. In Cloud Computing a database can be physically located somewhere in secure remote location and data can be accessed through clients computer using the database server to analyze and recover the data. This eliminates the need of a costly in-house equipments
and department. Cloud Computing make use of virtualized resources such as servers, computing devices and networks. Cloud Computing provider own the hardware and the providing host manage all the services to the clients according to their usage basis. On the
other hand Virtualization is creating virtual versions of technologies like servers, operating system, network resources and storage devices. Virtualization basically enables a single user to access multiple physical devices. In virtualization, either its
one operating system using multiple computers to evaluate database or a single computer controlling several machines. Here we will learn how Cloud Computing and virtualization are different from each other.
Cloud
Computing
The easily availability of computers has opened new doors in the field of information technology. Instead of creating own Data Center all the Data Center services can be acquired from IT server providers with outstanding IT infrastructure which is strong, flexible
and safe. The cost which either wise would have been invested in building a Data Center can be avoided with acquiring related services on a usage basis. Fees for the managed IT services is similar to the operating costs of a Data Center. Cloud Computing seems
attractive option, since it cuts a lot costs and also remove operating costs. In a traditional IT department equipments and staff are occupied in the peak hours, however in off hours they sat idle. Most of the servers are not operable in off hours, even when
they are operational its not necessary that they are giving their 100% of their potential. Also a Data Center services provider also needs to upgrade latest technologies in order to keep the data safe and secure. On the other side these services are provided
by Cloud Computing provider.
Virtualization
There are many types of virtualization, but all of them focus on usage format and control that improves efficiency. What this efficiency means is a single task running over multiple computers through unoccupied computer or a single terminal running multiple
tasks. One more advanced advantage of virtualization is hosting an application to many users, thus preventing several needed software’s from being installed again and again. Data is combined into a central computer from databases, hard drives and USB drives.
This process increase security and accessibility by using replication. In an IT company physical resources can be divided into many virtual networks allowing the Central IT resources to be available to all the departments via local networks. Computer devices
which are allocated to individual staff members or which are only dedicated to a specific software application are highly efficient and they are much more cheaper.
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3. The Difference Between Virtualization and Cloud Computing: http://www.erpsoftwareblog.com/2010/08/the-difference-between-virtualization-and-cloud-computing/
Brittany Meeks, Dynamics GP Sales and Marketing Assistant
As a newbie sales and marketing assistant at Custom
Information Services, I kept getting thrown technical terms that I was unable to grasp. That is until I did some research and discovered the easy way to understand and implement such terms or questions as, “What’s
the difference between virtualization and cloud computing?” Originally, I couldn’t even tell you the meaning of virtualization or cloud computing, let alone what the differences were. Since we implement and support these technologies I had to understand
the definitions quickly!
Virtualization is a computing technology that enables a single user to access multiple physical devices. Another way to look at it is a single computer controlling multiple machines, or one operating system utilizing multiple computers to analyze a database.
Virtualization may also be used for running multiple applications on each server rather than just one; this in turn reduces the number of servers companies need to purchase and manage. It enables you to consolidate your servers and do more with less hardware. It
also lets you support more users per piece of hardware, deliver applications, and run applications faster. Follow this link for more detail on virtualization VirtualizationWhitePaper.pdf
Cloud computing offers scalable infrastructure and software off site, saving labor, hardware, and power costs. Financially, the cloud’s virtual resources are typically cheaper than dedicated physical resources connected to a personal computer or network.
With cloud computing, the software
programs you use aren’t run from your personal computer, but rather are stored on servers housed elsewhere and accessed via the Internet. If your computer crashes, the software is still available for others to use. Simply, the cloud is a collection
of computers and servers that are publicly accessible via the Internet. Here is something else I found online which may be helpful in better understanding cloud servicesMicrosoft
Cloud Services.pdf
One way to look at it is that virtualization is basically one physical computer pretending to be many computing environments whereas cloud computing is many different computers pretending to be the one computing environment (hence user scaling). Virtualization
provides flexibility that is a great match for cloud computing. Moreover, cloud computing can be defined based on the virtual machine containers created with virtualization. Virtualization is not always necessary in cloud computing; however, you can use
it as the basis. Cloud computing is an approach for the delivery of services while virtualization is one possible service that could be delivered. Large corporations with little downtime tolerance and airtight security requirements may find that virtualization
fits them best. Smaller businesses are more likely to profit more with cloud computing, allowing them to focus on their mission while leaving IT chores to those who can do more for less.
Plainly, virtualization provides more servers on the same hardware and cloud computing provides measured resources while paying for what you use. While it is not uncommon to hear people discuss them interchangeably, they are very different approaches to solving
the problem of maximizing the use of available resources. They differ in many ways and that also leads to some important considerations when selecting between the two. Not only do we offer Dynamics
GP, but we also offer services for cloud and virtualization for your business applications. Our new website set for a September go live will have more information on this subject.