Reliability is also the subject of a debate that is difficult to settle. In a virtualised environment the loss of the network connection can cut access to multiple servers; but there could be a similar problem for a cloud set-up of the wide area network link goes down.

But there is a case for stating that the cloud offers greater resilience in the event of a problem, with the provider likely to have more options for using multiple servers or shifting to other data centres.

In addition, there will usually be more scalability in the cloud, with the scope for a rapidly and processing capacity without the time and cost of a big in-house investment.

This aligns with the flexibility that comes with the short term deals offered by cloud providers, sometimes with commitments of months rather than years, to make it responsive to what the customer needs.

But the fanfare around cloud computing should not distract from the case for virtualisation. Overall it's not clear cut, and depends on a series of value judgements determined by the nature and circumstances of the organisation's business.