The Private Cloud: Good or Evil?

Of course, there are concerns when it comes to cloud computing, with security being the biggest on the list. The use of the internet alone will instill shock and horror in IT heads and CIOs in the enterprise world - and perhaps rightly so as the recent outage of twitter due to massive Denial of Service (DoS) attacks have shown.

Still, since most people in the industry agree that the cloud is here to stay, the above IT heads and CIOs as well as existing and would-be cloud service providers have found ways to mitigate the drawbacks of using the internet.

The first group, the critical but determined IT heads and CIOs have defined the Private Cloud as a way out. In their version of the cloud world, there is (practically) no place for the internet in a corporate IT architecture: They propose to use privately managed network infrastructures such as IP Virtual Private Networks (VPNs) based on highly secure protocols such as MPLS or even dedicated leased lines or Ethernet links between enterprise sites and their usually fully owned data centers. Within the data centers the same virtualisation techniques are deployed as in the public version of the cloud. In this model the public cloud is faithfully replicated but completely separated from the private cloud. Since this model leaves very limited space for an external Cloud Service Provider, there has been a certain level of criticism regarding this approach as it appears to change very little compared with the existing "dedicated Data Center" model.

This is of course not quite fair. A large organisation can achieve nearly the same level of efficiency gains that the public cloud offers. Furthermore it is a logical continuation of the evolution that started with data center consolidation and application standardisation in the enterprise world. The next logical step is storage, server and application virtualisation which brings the model reasonably close to the mechanics of (public) cloud. Early adopters within the corporate world have already and successfully realised this scenario to an astonishingly high degree.

The second group mentioned in the fist paragraph, the cloud service providers, are effectively locked out of the game by the "fully owned private cloud" approach described above. Therefore, these players have put forward their own definition of the "private cloud". This model also makes use private network infrastructures, but it uses them to securely connect enterprise sites to a providers data center. Within this data center, Virtual LAN (VLAN) structures are used to separate individual private infrastructures from each other and from - god forbid - the internet.

The following figure illustrates this "shared private cloud" (Private Cloud type A) and the "fully owend private cloud" approach (type B).


We would argue that Type B makes some sense for very large organisations which are big enough to leverage scaling effects within there (standardised) IT infrastructure. Very ofter these organisations will stick to private data facilities anyway, whether for sensible reasons of out of self preservation instincts of the IT department.

Type A on the other hand makes sense for smaller or less IT centric organisations which perceive a tangible benefit associated with the increased security of the private cloud which of course has to exceed the additional cost incurred for the more expensive private network infrastructure.