I thought you’d never ask. The virtualization market is confusing to some because they are not exactly sure what virtualization is. I think a simple diagram will help, so try this:
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The Virtualization of a Server Blade

The server blade has cpu, memory and i/o capacity that can be shared. What the diagram shows is the virtual machine software (it’s called a hypervisor) taking up 5% of these resources and managing 3 virtual machines, with resources allocated 35%, 20% and 40% respectively. The scheme shown is a very simple one which runs 3 different operating systems, but divides cpu, memory and i/o in exactly the same ratio. There is nothing to prevent varying the ratios so that one VM had, perhaps, 20% of cpu, 40% of memory and 15% of i/o.

(Note that you could also partition disk space, but the assumption here is that the server blade has no local disk and is connected to a SAN).

The VM would normally be configured to cater for its particular workload. If you were running, say, 3 mail servers on the blade you would, naturally, share the resources equally. But if you ran a mail server and a DNS and an Apache server then you’d try to share the resources in a way that matched the needs of these applications.

As soon as you add further sophistication, so that, for example, if the blade fails then you immediately fire up new instances of the VMs then managing it become more complex. That requires management software that co-ordinates the behaviour of a pool of blades.

The management of virtualized resources is complex enough to require an organization to proceed with some caution, implementing virtualization bit-by-bit, establishing management procedures and processes as it goes.

This is a posting in the Virtualization Focus Series. Click here to see an index of such postings.