Public vs. private clouds

Find out the difference between public and private clouds and get help determining which of the two would best suit your enterprise.

This tip describes the difference between public clouds and private clouds, according to Internet service provider Star, and highlights which cloud is better suited for differing business needs.

Public clouds
First and foremost, public clouds are accessible from the public Internet. They can be secure in terms of access methods, encryption and access control. They can also be unsecure, but no more so than a publically accessible website, which is probably the easiest way of picturing public clouds.

Servers and application services are billed on a per-use basis but accessible from a normal Internet connection. This doesn't mean to say that they are unsecure by definition. You may have high levels of security protecting public cloud services, but in the eyes of data protection bodies, financial service authorities and the like, a publically advertised service is vulnerable to attack either intentionally or by worm-type viruses.

Public cloud services are suited to a wide range of verticals; retail, for example, will happily exploit the advantages of pay-per-use storage and bandwidth for rich media and images for their online product catalogue. Small to medium enterprises welcome pay-per-use mail, calendaring and conferencing facilities. It allows them to shop around, chop and change and avoid single vendor lock-in.

Domain specific, intellectual property and sensitive data are three key areas that make companies nervous when it comes to public clouds. The subject of "Where is my data?" also unsettles a number of people. The fact is that, in terms of the evolutionary scale, we are in the early stages of utilising public clouds in a way that can be compared to on-premise systems.

Private clouds
Private clouds offer all the advantages of pay-per-use billing that we see in public clouds but with guarantees around key aspects like:

  • Bespoke design and architecture
  • Secure access methods using private connectivity
  • The location of your data
  • The people that can access your data

The transition to private clouds for large and small organisations is in full swing.


Matt Mould, Head of Solution Architecture, Star,

The transition to private clouds for large and small organisations is in full swing. Traditional hosting companies are changing their strategy by providing monitored and managed environments based on pay-per-use, scale up and down infrastructure services.

It's likely that, in comparison to public clouds, companies will remain locked into a private cloud supplier for a long term contract (12-36 months). The value of the contract, however, can fluctuate month by month depending on the demands made on the hosted infrastructure and/or services, e.g. a farm of virtual private servers and email seats.

Financial services, insurance, energy and government are well suited to private clouds because of three key reasons:

  1. Compliance and regulation can remain intact
  2. The technology jump needn't be so severe
  3. Immediate cost benefits can be made by consuming services on a pay-per-use basis

Many people are saying, "Virtualise today, cloud tomorrow." This is true for a number of organisations with core business applications that aren't ready to move to a loosely coupled or service-oriented architecture (SOA) that will ultimately unlock their application landscape from being interdependent on each other.

Many organisations are striving for the following high-level strategy ,which is smack bang in the middle of private cloud provider's services:

  • Virtualise on-premise in readiness of moving to a private cloud
  • Moving from a traditional outsourcer to a private cloud hosting partner offering pay-per-use services and virtualisation technology
  • Engage ISVs (independent software vendors) to help them develop their way out of traditionally hosted applications and base more core business systems around secure Web services and centralised messaging (managing the flow of information centrally for critical applications), allowing their business to become accessible, anywhere, anytime, from any machine

You'll notice that the last point could be read as a strategy to move away from private cloud providers. It's true that once an organisation has moved to Web service-based systems and centralised messaging, services could be hosted in the public cloud, but security concerns will always be an impediment for some organisations. Therefore, the private cloud will continue to dominate the hosted services space for a large proportion of companies.

Matt Mould is the head of solution architecture at Star and a contributor to SearchVirtualDataCentre.co.uk.

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