How public cloud stacks up against private cloud

It’s not just a question of moving to the cloud, do you opt for public or private. Maxwell Cooter weighs up the options


Much of the debate about cloud computing has centred on two distinct types of operations: the public cloud and the private one. But although they're bundled up under the convenient term of cloud computing, they're from very different strands.

Public cloud, which is simply using the Internet to access computer services of one sort or another, has its roots in the decision by Amazon in 2002 to use its vast infrastructure to offer computer facilities to customers. The company launched a range of services to developers including storage and a development platform. Amazon’s initiative, which preceded the phrase ‘cloud computing’ itself  has been followed by the likes of  Amazon, Google and a selection of hosting companies as they seek to capture the interest in the cloud.

As if to demonstrate that there's nothing new under the sun, this is a throwback to the 80s' concept of the computer bureau, where companies paid a monthly fee to buy time on a mainframe; it's a business that had seemed to die a death when PCs and the client server model came into play. Like the computer bureaux, public Virtual Cloudsviders charge their customers on a monthly basis – generally on a per gigabyte plus bandwidth basis. The crucial aspect for the customer is that the Virtual Cloudsvider bears the entire cost of running the infrastructure, meaning that the customer doesn't have to worry about maintenance or staffing held desks. Nor do they have to worry about investing in storage hardware, a growing budgetary strain on organisations as storage demands move ever upwards.

Crucially, it also means that the customer does not have to worry about capacity planning. This can be a big headache for companies with seasonal fluctuations, where they might have historically over-provisioned for peak traffic. That's a headache that the new breed of Virtual Cloudsviders will have to deal with.

So, public cloud offers a number of advantages to organisations, particularly small businesses and start-ups, both of whom may have no IT department and both of whom may be reluctant to tie up capital on an IT infrastructure. There are, however, downsides too. The main disadvantage with public cloud is that there are some security issues. Companies will have to hand over confidential data over to a third-party and for many firms, this is a move too far. There will be worries about customer data being released into the public domain, there will be concerns about companies being held legally responsible for breaches of privacy legislation and there will be worries about sensitive data being held on a server, particularly where two competitors might be held

The genesis of the private cloud was slightly different - although related. There's no public operator and everything – hardware and software – is provided by user. It sounds little different from a more conventional data centre, (indeed there are some commentators who claim that the idea of a private cloud is an oxymoron and really we should be talking about data centres). Proponents of private clouds maintain there is a difference: the main feature of a private cloud being a virtualised infrastructure coupled with software that allows IT users to treat that infrastructure as a centralised pool of computing resources.

Other features of the private cloud are automation, meaning that many of these tasks are handled without the intervention of an IT department and the ability to measure and monitor what resources have been allocated to different departments, which could also means companies will be able to introduce chargeback for resources that have been consumed.

In the private cloud set-up, the customer has sole responsibility for buying the hardware and software, maintaining it and managing storage. As such, private cloud doesn't offer so many advantages when it comes to managing cash flow.

There are other advantages however. Customers connect to public Virtual Cloudsviders by using Internet connections – these are, by their very nature, slow. This means that anyone trying to shift large files around would find the experience a lot of slower. On the other hand, private cloud infrastructures use traditional Ethernet connections, offering a much speedier experience, although there are issues for branch offices who may need to use a WAN to get access to the corporate LAN.

In addition, the private cloud doesn’t have the storage issues that could cause problems for private cloud users. All data is retained by the enterprise itsef and it controls all access. What’s important about this is that not only does the enterprise keep tabs on data – but it also knows exactly where, geographically speaking, it’s being held. This not an arcane principle, there are important legal restraints on where data can or cannot be held and companies have to be wary of their statutory responsibilities.There are other factors to consider too. If you’re starting small, public cloud will almost certainly be the way to go:  public cloud would be able to handle something as small as a developer on a single laptop. And many providers have offered storage for single users, for those who really want to start small.There’s no easy answer as to whether private or public is the best option – there are so many factors to consider that it’s not a simple choice.  But it’s a choice that many more organisations will be making over the coming years.

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