Cloud commuting or cloud computing—as it is popularly called—must necessarily take cognisance of Virtualisation. Today, every organisation has virtual machines that need to be backed up and recovered. But, how are these virtual machines different from physical machines? A basic understanding of the concepts will go a long way towards easing the process of backing up or recovering organisation data to or from the cloud.
What is Virtualisation?
It is true that virtualisation has been around for many years now. It was first used in 1960’s and remained a feature of mainframes for a long time. It is only in the last few years–with the emergence of desktop virtualisation, network virtualisation, and later the cloud—that virtualisation has entered mainstream computing. A close look at what the term means will reveal that virtualisation is an umbrella concept. It is used in different contexts to refer to different things in a production environment.
Desktop virtualisation is the process of running multiple virtual desktops on a single PC. Each virtual desktop will contain its own operating system and applications and can be configured to load up on appropriate user authentication. Application virtualisation is the process of separating the application from the operating system and running it within a “sandbox” that can reside on a remote server or stream in from a remote server.
Server virtualisation, as mentioned earlier, allows many virtual machines to run on a single server. The different virtual machines share CPU, memory, storage and networking resources. Storage virtualisation is the process of grouping together physical storage using software, so that all the storage devices appear as if they were a single storage drive. It must be noted here that virtual storage is not the same as the virtual machine. The virtual machine is a set of files that run in the server box to create an operating environment, while virtual storage runs in memory on the storage controller using software to create the impression of a single storage repository. All the files in storage may or may not be present in the single server.
Cloud vendors exploit these two virtualisation features to make their services scalable and redundant. Network virtualisation is the process of using software to perform network functions. This is achieved by decoupling the virtual networks from underlying network hardware and using software switches to move data around.