Public cloud services are often compared to utilities. Indeed, back in 1999 and 2000 the concept was often referred to as "utility computing".
Instead of paying for a vast IT department to look after servers, organisations would be able to access computing power simply by plugging in and flipping a switch. That, at least, was the idea, but it proved to be a whole lot more complicated than that to implement in reality.
Nevertheless, if you buy the utility computing analogy, private cloud services don't seem to have much of a future. As public cloud absorbs more and more services into itself, running things in-house becomes a minority play. So, is private cloud dead in the long term?
"No I don't think it's dead, but I do think public cloud will be the default way of doing things," said Mark Ridley, group technology officer at venture builder Blenheim Chalcot Accelerate, speaking during a web seminar hosted by V3's sister publication Computing on Thursday.
Ridley describes himself as a convert and a "public cloud evangelist", having moved an entire data centre to shared tenancy facilities in a previous role. He believes that for most workloads the public model will make more sense, but not for all. Companies with large-scale operations may find it cheaper to retain infrastructure in-house.
"There will always be organisations for whom private cloud will make sense because of the economics. The prices you can get by buying in bulk will outstrip what you can achieve by buying from the public cloud. If you're at that point then private cloud is better."
There are other factors too, such as the variability of the workload.
"If you have very stable demand and you don't need the elasticity, if you aren't planning to scale significantly in the future, if your funding model doesn't favour operational expenditure then you will probably use private cloud which is best suited to a non-elastic model of service and investment," said Ridley.
"But if you are an internet facing company where you expect significant growth or where the demand changes throughout the day or seasonally then I think public cloud will outstrip it."
Compliance requirements will also favour the public cloud, he believes, as the current checkboxes approach offered by providers evolve into broadly accepted standards.
"If you're selling a b2b service and going through lots of compliance checks it will be easier to say ‘I'm with Amazon or Microsoft or Google and here is my box-ticking exercise. It will be easier for vendors and consumers to understand the compliance measures in place."
For the foreseeable future the mixed model will prevail, however.
"There will always be a place for private cloud but public cloud will continue to grow," Ridley said.
A recent study also backs up Ridley's assertion that at large scale and high levels of utilisation, private cloud is likely to be the cheaper option.
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