Peter Risdon

Tim has a piece up at Forbes talking about the relative costs of local storage and the cloud. I think it and the comments that follow at the time of writing miss an important point about the cloud.

We’ve had remote servers in data centres for decades. We’ve had at least some integration between different types of client platforms for decades, though Microsoft has done its best to inhibit this interoperability. Neither of these things are cloud computing.

If it means anything, a computer ‘cloud’ is a network with more than one physical computer and more than one storage device, an integrated control system and a high degree of virtualisation and redundancy. You can string together pieces of hardware so they look and behave like a single logical system, you can operate multiple virtual machines on one hardware system (Amazon’s cloud uses Xen, for example). If you’re really feeling good you can combine these two approaches. And you can often do these things using a nice control interface. The physical reality of the hardware and the logical structure of the system have been separated. Adding new hardware adds to the pool from which the virtual, logical units are constructed.

This means that cloud computing can’t be directly compared with a (more primitive) local computer and its hard drives. Cloud computing is intrinsically more robust and more expensive. It’s also far more flexible because you can add new nodes (computing units, storage units) or remove them as demand fluctuates. Many cloud services charge by the hour to reflect this flexibility.

These techniques of high redundancy and virtualisation have been around for years. I was hosting on a network of FreeBSD servers using jails for virtualisation for years before any marketing executive dreamed up the label ‘cloud computing’. Like ‘data mining’ before it, this is a more a marketing than a technical term; virtualisation and redundancy have long been found in well-designed systems. As marketing terms tend to, ‘cloud’ has now stretched to the point where some smaller IT businesses offer their own ‘cloud’ services that are actually based on single servers and not cloud computing at all. They are simply services housed in a data centre rather than onsite.

Tim’s point is that local storage has been getting cheaper at a faster rate than bandwidth. But then, these storage savings are also available to cloud providers. ‘Local’ storage can be accessible from any connected devices – all you need is a static IP address or a dynamic DNS service and you can host them from your bedroom. But they’re not offsite, which matters when you’re burgled or your bedroom catches fire. Expanding the system to meet a temporary upsurge in demand means buying new hardware and being stuck with it when demands falls back again.

Google can offer very cheap access to highly redundant cloud-based services like GMail because they monetise in ways other than direct charging (though GMail is also available as a chargeable service). But if you want to run your own cloud-based system, hiring the components from a cloud provider, it will be more expensive than operating a local workstation. This says nothing about the future direction of computing. A proper cloud system simply isn’t comparable with a single computer.

For what it’s worth, my view is that the separation between physical hardware and logical systems will continue to increase.