Server virtualization and cloud computing are common parlance in the IT industry, but the concept of private cloud architecture is relatively unclear and fraught with confusion. So I would say that the shortest definition can be, 'Virtualization on top of a high performance computing (HPC) platform'.
The fabric of virtualization has its limits. For example, there is little flexibility in scaling a virtual machine. The scaling will be always limited to the maximum resources available on a particular physical server. For instance on a 24 core server with 32 GB RAM, you cannot have a virtual machine which has more than (or even equal to) 24 cores and 32 GB of RAM.
However, if there are 50 such servers, then you technically have 1200 Cores and 1.6 TB of RAM. But if an organization needs a machine with higher specs from its virtual infrastructure, say 50 cores and 64 GB of RAM, it's just not possible. The organization has to buy a new server with more than 50 cores and 50 GB of RAM. This can be used as a physical box or to create a virtual machine.
With infrastructure as a service (IaaS), an organization first aggregates its data center as a single resource pool, and then starts provisioning virtual machines on it. This is similar to creating an HPC platform which integrates all your existing resources in a single pool and then running a virtualization layer on top of it.
Very few companies provide full-fledged private cloud architecture. One such commercial offering is Enomaly, while Eucalyptus is an open source variant that has gained attention. You have to keep a few things in mind while deploying private cloud architecture:
Server architecture: This technology runs on the Hypervisor-based virtualization. Servers need Intel VT or AMD Pacifica features to run as part of the private cloud architecture. So it's essential; that you rule out old servers.
Selection of cloud middleware: It's best to opt for a private cloud architecture supported by your existing server virtualization platform. A XEN user can select between Ubuntu Enterprise Cloud or Enomaly. If you are a VMware fan, then sticking with VMware based private cloud architecture is a better option. Microsoft Hyper-V users will have to wait for the time being. Microsoft has promised to launch its Dynamic Datacenter Toolkit, which will let users build private cloud architectures based on Hyper-V.
It is important to assess whether you require a hybrid cloud, and whether your cloud platform supports public cloud architecture. Eucalyptus which runs inside the heart of Ubuntu Enterprise Cloud is Amazon EC2 compliant, and can connect with EC2 to form a hybrid cloud. Similarly, we can speculate that Microsoft's Dynamic Datacenter Toolkit will integrate well with Microsoft Azure.
About the author: Anindya Roy is a tech evangelist at Netweb Technologies, and has worked on open source private cloud platforms. His specialization areas include HPC, cloud computing, and virtualization. Roy also has an extensive experience in application evaluation as well as testing.
(As told to Jasmine Desai.)