What is Cloud Computing ? and Why?
Question: > **Possible Duplicates:**  
>  [What is Cloud computing?](http://stackoverflow.com/questions/108037/what-
> is-cloud-computing)  
>  [What is cloud computing?](http://stackoverflow.com/questions/1830142/what-
> is-cloud-computing)

Sorry for asking some Simple Question. But I cannot clearly understand the
needs of Could Computing. or better to say I am confused about what actually
Cloud Computing is. I've seen a lot of articles on this topic. But they were
non technical and I cannot understand it properly.

Is Cloud Computing a replacement of dedicated Server ? If yes then why would I
use it instead of dedicated Server ? What is Pay per use ? The Pricing Plans
looks like VPS Hosting Plan Charts !! If I need a Service (e.g. it might be
some kind of XML service) heavily used by multiple Applications. I'll put Only
the Service in a dedicated server and apps might be hosted in Shared Hosting
(doesn't matter). Wait a min.. Does it mean My Application hosted on a Cloud
will get CDNs like Google, AOL have :( Sorry I am Confused.

I see in Google App Engine I am restricted in Python and Java Only (thats the
reason I was not interested in Google App Engine much from when it released).
and in an article I saw in Amazon there is no persistent storage. Hmmmm What
does it mean ?? Will I've to reupload everything ?? I see I need to start VM
Images there .. So do I need to pay by the time frame when my image was Up ??
But I find no reason to my Apps non-24hrs.

Sorry I am confused. Please Help me to figure it out.


Answer: > Is Cloud Computing a replacement of dedicated Server ?

Sometimes

Depending on the service offered you upload either a virtual machine image
containing all the stuff you want to run, or a single java program. It runs,
you (and your customers) use it.

> If yes then why would I use it instead of dedicated Server ?

You need a database server today - instead of waiting for Dell to deliver it,
then for you to check out the HW, install the OS, configure it, get the
network working, cool it, manage it, secure it - you just click a couple of
buttons on Amazon/Google and your server is running.

Then your service takes off and you need 100 servers tomorrow, or you have a
business model that needs 100 servers on the last day of the month but 1
server all the time. Cloud computing lets you create new servers by the
minute.

> What is Pay per use ?

You pay for how many cores/how many IP addresses/how many machines you use,
for only the time you use them. Unlike buying a machine and OS license for
life.

> Amazon there is no persistent storage.

Amazon also sells storage with their S3 product which you can use either from
your cloud server or your desktop - I suspect their cloud offering uses S3 so
you buy storage separately.

> But I find no reason to my Apps non-24hrs.

You don't have to, most cloud users are using it to drive their website based
business - stackoverflow could (but doesn't) run on the cloud. SO 24x7
availability is important - this is one of the advantages of the cloud, if a
machine dies your image is instantly started on another machine possibly in
another data center.

Others use it for heavy computing jobs and just buy the time on 100s of
machines to complete the calculation then quit them.

