Public Clouds are readily available from Amazon, Google, Microsoft, HP, Dell & Memset amongst others. These Public Clouds use Virtualisation technology to store multiple instances of virtual machines on large pools of physical servers within geographically dispersed data centres. This will mean that customers will be running their virtual machines alongside other customers on the same physical server without any knowledge of who the other customers are or what they're using it for.
Not everybody wants to share the hardware that their systems run on with unknown neighbours. However, people do still want to take advantage of the efficiency savings derived from using the Cloud. That’s when you seek out a Secure Private Cloud. That’s not to say Public Clouds are insecure, they are and work very well with the hypervisor separating virtual machines from one another to all intense purposes the same as if they were on separate physical machines. So if the hypervisor keeps you separated what’s the big issue? Well, legislation may mean that if you store sensitive data you may not be allowed to keep that data on hardware you share with others. Alternatively you may work with partners who have strict security procedures from preventing you from using shared hardware.
So who would be in the market for a Private Cloud? You might be a government organisation or partner that holds large amounts of data on the population and are enforced by legislation to not share hardware with unknown partners. Banking, insurance and investment firms also hold large quantities of sensitive data on people’s financial affairs. In some cases these are bound by legislation and in other cases bound by perception of their service to not used shared hardware. Military equipment suppliers and sensitive R&D Engineering firms who have experienced sustained cyber-attacks in recent years would also be very reticent to share their hardware with anybody else. Alternatively you might just err on the side of caution and want the peace of mind that you have your systems only running on equipment designated to your organisation.
So the features of a Private Cloud are no shared hardware. This can include having servers, storage and network equipment in a data centre specifically separated from the rest of the equipment. This can also include physically secured in separate rooms or cages to prevent unauthorised physical access.
Some Private Clouds are even operated entirely in house by companies with no outside influence on their data centres. Different business divisions or branch offices can access the Cloud resources as and when they need them. This lets systems administrators and developers provision more servers in a matter of hours rather than weeks as would be typically involved with procuring physical servers. However, these types of Private Clouds are typically only suitable for large organisations that can support both operating the required data centres and retaining the specialist staff to administer the virtualization of servers, network and storage technology.
Most small to medium sized enterprises needs for Private Clouds are better served by specialist providers who have the in-house skills required to deliver the Private Cloud solutions but can still keep the costs in reasonable terms.