Cloud Server's

[Sim]

What is a Cloud Server? I can't figure out the concept of it.

[Jordan Palmer]

http://www.google.co.uk/search?hl=en&defl=en&q=define:cloud+servers&sa=X&ei=c5krTY6vO8q5hAfX0dSSCQ&ved=0CCkQkAE

[Zeggy]

Cloud servers are virtualized servers, allowing a single physical server to run multiple instances of a cloud server. (Similar concept as a VPS)

Because it's virtualized, these servers exist as a file (or multiple files) on hardware. This means the cloud server can be moved between different physical servers, or copied, etc. The advantages of this for a web server is that you can duplicate the cloud server and deploy it among servers all around the world very quickly. You can also scale the hardware, adding more ram, more hard drive space, more resources spread among many pieces of hardware over a network.

Cloud hosts take advantage of this by offering plans that you pay for according to how much you use, allowing you to have a server that uses far more resources than a traditional single server could handle.

For an example, take a look at amazon web service's EC2, probably the biggest cloud hosting service in the world: http://aws.amazon.com/ec2/

You can see that you simply pay for "instances" (virtualized servers) by the hour.

Another example is google app engine. You can see you simply pay per unit of resources used, instead of having a fixed monthly cost: http://code.google.com/appengine/docs/billing.html#Billable_Quota_Unit_Cost

The pricing difference is also important. In traditional hosting, you pay in advance for a month of service, whereas cloud hosting you generally pay for how much you use. Using an analogy, traditional hosting is like having a monthly mobile phone contract, while cloud hosting is like getting a bill at the end of the month. Of course, not all hosts follow this kind of payment scheme, there are always exceptions.

An example of when you may want to use cloud hosting is when you need to support massive amounts of traffic, even for a very short time like a few hours, like if you get slashdotted. With cloud hosting, you can simply add more resources and pay for the increased usage for those few hours, as opposed to upgrading your hosting plan or buying a new dedicated server like in traditional hosting.

[a_bertrand]

I would simply add something to Zeggy post. Depending on your application, different functions could run on different servers of the cloud and therefore work in a more load balanced way. A cloud VPS the whole system could be migrated but cannot be easily split, where an appropriate application (read developed with the right API) could run as "pieces" over the cloud. For example if you have a "report" function running it could use the physical host A and in parallel a "order" function on a host B. That could vary over the time with the load of the different nodes of the cloud and the requirements of the application(s).