There is a raging debate within our industry about private cloud vs public cloud computing.

With this in mind I’d like to clarify what the differences are in approaches to the cloud, as the arguments that either private or public cloud are the best solution are just plain confusing, and in our opinion factually incorrect. To say one option trumps the other is incorrect because they are only two of many different ways to deploy IaaS (infrastructure-as-a-service) type cloud solutions, and these just happen to span the continuum from private to public cloud (and in fact into old world hosting services). Interestingly enough Gartner was reflecting our own thinking at their latest symposium in Sydney last week.

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The basic deployment options for IaaS in the cloud

So, let’s get clear about what these different deployment options are, and what the benefits or drawbacks of each are.  A quick note, I am not going to get into definitions for each, you will find many contrary opinions all over the web; instead I’ll describe them as use cases to show the differences.

Private cloud on-premise:

Companies that go this way build their own elastic, cloud environment within their data centre facilities behind their firewalls. They are the only user of this cloud.

Generally speaking the benefits of this are seen as more control of the solution and data, and better security (but this is up for debate), the downside is limited financial benefit (you have all the investment, all the ongoing maintenance and all the staff).

Private Cloud off-premise:

As above, you have your ‘own cloud’, but this may or may not be in your data centre (you can co-locate these, for want of better words), but the cloud is built and run for you by a service provider.

The benefits of this approach are again control and security, but you also get more gain as you have outsourced the management to a specialist. The downsides are again on the financial side. While better, you still aren’t getting the true benefits of scale.

Shared private cloud (trusted clouds):

This is a true cloud environment in that the computing resources are shared with multiple tenants in a third party’s data centre, but you connect to it over a private data network. By combining network and computing virtualisation technologies, the cloud essentially appears like any other server on your WAN.

The benefits of this approach are definitely security (private networking combined with a specialist provider of cloud), pay for what you use, flexibility and agility of cloud resources and performance (as the network and compute resources are managed to service levels). Shared private clouds are normally provided by the local telco so the physical data centre is within your region. The drawbacks are a little less flexibility, slightly slower provisioning (it’s slightly more complex to set up), and cost (these clouds aren’t as large as public clouds so there is some scale disadvantage).

Shared public clouds:

Think Amazon, these are shared multi-tenant computing environment in a third party’s data centre that you connect to over the internet.

The benefits of this approach are elasticity (scale up or down as demand changes), pay for what you use, rapid provisioning, and the ease to sign up for and use. The downsides are less control of where the data is (or which data centre) and network issues through distance or using the public internet.

All approaches have a place

At Gen-i we don’t believe a rigid approach to thinking about cloud is best. Each business that moves to the cloud should think through its needs and adopt the best approach for them. The same is true for the different computing functions you have, some are well suited to being in the cloud, while others are not.

But like I said before, there are varying views on this, so feel free to share your thoughts below…