Data Center

What is a Private Cloud & Difference between a Private Cloud and Server Virtualization

You should be familiar with Server Virtualization, which is basically a set up to decouple the applications from their physical servers using an abstraction layer called ‘Hypervisor’ that enables Multiple Applications + OS (Virtual Machines) to reside within a single server. Server Virtualization isolates the various Virtual Machines (VM) and allocates / controls the resources that can be utilized by each VM. Server Virtualization allow dynamic provisioning of resources based on their demand and also allow Virtual Machines to migrate between one Server to another (or) occupy multiple servers, as required.

But that’s exactly what a private cloud system is meant to achieve, as well. So, what’s the difference then between a private cloud and server virtualization?

“A private cloud is a software infrastructure that enables end-users to acquire, configure and ultimately release data center resources on-demand, using automated self-service tools and software services within an enterprise’s data center” – Five Steps to Enterprise Cloud Computing (White Paper) by Eucalyptus Systems.

Most of the existing infrastructure in any company is over provisioned. People always buy more than what they need. But these resources are spread across the enterprise in silos (across multiple departments). That’s why they are all consolidated in a data center and Server Virtualization is adopted. Server Virtualization gives resource centralization, optimal resource utilization and some redundancy against individual server failures. This also takes care of re-provisioning resources during seasonal bursts in traffic.

But what if the demand exceeds all the existing resource capacity? Can you add additional servers / storage in minutes? Can you port your applications to a public cloud just to handle sudden bursts in traffic? Do you have a centralized management interface to provision & manage individual resources like servers, storage units, networking, etc? Or better, can the users themselves provision the additional resources they might require?

Welcome to the Private Cloud.

You should be aware of Public Clouds where infrastructure is already set in place by external service providers and you just need to port your application and run it on their infrastructure. You are generally charged on the amount of bandwidth / processing resources used and not on how many servers you occupy, time taken to complete the task, etc. That makes it easier for people to buy just the amount of resources required and buy them only when they are required. With Public Clouds, its possible to roll back or scale up when the task is over / additional resources are required.

So far so fine. But there are some issues with using public clouds, especially for enterprise companies. First, most organizations would like their data to reside on their own infrastructure within their own premises, primarily for security / privacy reasons. Second, there are limited options for customizing hardware configurations. Third, interoperability between the enterprise applications and public cloud infrastructure needs to be tested prior to  implementation. Fourth, there is always a potential cost overrun (in the long term) and under-utilization of enterprise computing resources.

That’s one of the reasons why companies find it necessary to build and manage private clouds within an organization.

A Private Cloud utilizes the existing infrastructure in an organization and runs on dedicated hardware within the organization’s data center. All forms of virtualization (including server virtualization) are a part of private cloud infrastructure.

“No single vendor today provides all of the software required to build and manage a real private cloud – That is, one with server virtualization, storage virtualization, network virtualization and resource automation / orchestration”Computer World article on Private Cloud.

Advantages of a Private Cloud over Server Virtualization:

1. A Private Cloud can scale up / down swiftly (within minutes or hours) – It is possible to add a virtual server or even a physical server quickly using predefined templates / predefined configurations. It is also possible to automatically provision additional infrastructure like networking devices, storage devices, security devices/ policies, etc without having to individually configure the settings for each device.

2. Users can themselves allocate the resources they might want (from the available resources) using a self service portal/ console. And private cloud gives them the resources with which they can do so. So, Virtual Machine’s can be automatically allocated to the user upon their request – Imagine the time saved due to this!

3. While the user takes the additional burden of allocation of resources, application deployment & management, the IT department gets more time to concentrate on core infrastructure related functions like Capacity Planning, Infrastructure Creation, Archival Storage & Backup, Network Security policies, Interface Customization, etc.

4. It is possible that even with the consolidated infrastructure of the private cloud, the demand (at times) might exceed the installed capacity. A private cloud provides (or should provide) for the bursting of this additional traffic into public clouds (automatically) so that seasonal traffic bursts can be managed, with a small additional investment. So, interoperability and standards for public and private cloud computing is critical and it is currently available in a limited way.

5. Private Clouds provide (or should provide) audit/ accounting tools and Internal as well as External compliance can be achieved easier. Further, private clouds can adhere to strict SLA’s – Service Level Agreements.

6. Private clouds enable interoperability between resources present at multiple data centers. It is possible to migrate applications over to other data centers when one of them cannot manage the demand.

7. Ideally, multi vendor hyper-visors, multi vendor servers, multi vendor network equipments, multi vendor storage equipments, etc need to be managed using a single console with a private cloud. Practically, it happens with multiple software/consoles but this is the vision of Private Cloud Computing.

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