virtual machine and cloud computing [closed]

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hi everybody I'm very new to IT fiel开发者_C百科d can anybody explain me relation between virtual machine and cloud computing . In my firm they using a private cloud using ubuntu eucalyptus tool . They uses KVM. when ever i demand the resource they says we will give u the virtual machine is cloud computing means providing virtual machine as i study cloud computing over the net it sound like a different technology . More important i want to know does the specification(characteristic ) of virtual machine depend on the physical machine ? which they are imitating or we can provide our specification such as making a virtual machine of 100 GB storage while the physical machine has only 20 GB hard disk?or is it possible to make a virtual machine a virtual machine 0f 4 gb RAM while physical machine is having ram of 128 mb please explain me this concept I'll be thankful to all of you forever

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Here it is in a nutshell:

A cloud is built up of numerous physical machines (the hardware). Each of these machines then run multiple virtual machines, which is what are presented to the end-users.

Virtual machines are only limited in the way that their specifications cannot exceed that of their host (the underlying physical machine).

So no, if the physical machine on which your virtual machine runs only has 20GB of harddrive space, you cannot ask them to create a VM with 100GB of disk space. (The same applies to RAM).

That being said, the way storage works on the EC2 (Amazon Compute Cloud) is a bit different. The storage is done offline, so in that case it would be possible to request drive space that exceeds the host, but again not exceeding the physical size of the actual place where the storage is done.

Furthermore, the restriction placed that Vitrual Machines cannot exceed the host capabilities also applies if you have multiple VMs running on the same host. In that case, the shared capabilities of the VMs cannot exceed that of the host. For example, if you have 4GB of RAM on the physical machine, then you can have 2 VMs each with 2GB of RAM.

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Virtual machines means sharing the resources of a single physical computer among several different virtual computing environments - effectively, one computer pretending to be several computers. Obviously, you can only share whatever physical resources you have so if the physical machine has 12Gb of RAM, then you could have virtual machines that use up to 12Gb combined; however, you could distribute the 12Gb as you like, for example with one computer having 4Gb while the rest only have 1Gb. Similarly with hard disk space and processing power.

Cloud computing is effectively many computers pretending to be the one computing environment. In practice, the computers making up the cloud system will also be virtualised in order to maximise the resources of the physical computers.