Know your clouds

Private vs. hybrid vs. public and IaaS, SaaS, and PaaS. Here’s my primer on how to start figuring out what’s what with clouds.

First, you do get that a cloud is not just a bunch of servers, right? To refresh your memory, the key difference for users is that cloud computing services are delivered as a utility. Got it? Good.

Moving on, there are three basic ways clouds are presented to users. These are public, private, and hybrid. If anyone can access a cloud service simply by using a credit card or for free — for example, Google’s Gmail, Microsoft’s Office 365, Dropbox file storage, or Amazon Web Services (AWS) — then it’s a public cloud.

In a private cloud, you’re simply providing your own cloud-style services from your own data center. You can do this by using the same cloud programs as the big companies, such as Microsoft Azure, OpenStack, VMware vCloud, or on a scale you can run out of your server closet using programs such as ownCloud. Any way you do it, if you own and control the hardware and software, it’s a private cloud.

Say you want the flexibility of a public cloud — after all, Google can afford more servers with Google Compute than you can in your data center — but you still want most of your data and programs on your machines under your control, then you want a hybrid cloud. Typically, you’ll run your day-to-day work on your servers, but if there’s a sudden up-tick in demand, you’ll transparently call on the resources of an allied public cloud.

That’s how you basically run clouds, but there are three fundamental types of cloud services: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

IaaS: This is the building-block for all cloud services. In IaaS, users are given access to physical, or more typically, virtual servers. These in turn provide file storage, virtual machines, and servers. With IaaS you’re getting basic server services that automatically expand or contract depending on your company’s use of these services. Many cloud-providers provide these services, such as CSC CloudCompute.

PaaS: Take an IaaS and add a software development stack and you have a PaaS. There are numerous variations on this theme. Personally, I think of these as living between IaaS, which provides basic IT services; and SaaS, which provides a pre-packaged application. A PaaS can be built on top of an IaaS and, with sufficient software maturity, a PaaS project can turn into a turnkey SaaS.

SaaS: Everyone uses SaaS. Many of the most popular online software programs such as e-mail/Gmail, basic office suite functionality/Google Docs, customer relationship management (CRM)/Salesforce, etc., are cloud based.

SaaS started as a variation of client/server computing, then took a left-turn into application service providers (ASP) in the late 90s and early 00s. SaaS became mainstream because of the cloud architecture’s elasticity. ASPs, which had been limited by the need to manually set up servers could never meet user demand. With a cloud, SaaS can automatically deliver its application goods in the face of all but the strongest usage spikes.

Another shift that empowered SaaS is its use of the Web browser as the universal user interface. At one time, every ASP application had its own front end. Today, the Web browser is the default interface. This, in turn, means a SaaS application can “run” on almost any platform.

There are other kinds of clouds but more often than not if you look deeply into what’s actually being offered you’ll find that it will fit into one of the three above-mentioned categories. For example, Management-as-a-Service (MaaS) is really just system management in SaaS form, but there are also more than a dozen kinds of MaaS, which appear to be more marketing hype than technology reality.

So long as you keep these three types of cloud deployments and three kinds of cloud clearly in mind, you won’t go too far wrong.


  1. Good read.
    Many cloud computing consulting companies are there providing proper training to know and learn cloud. I think this post will be very helpful for beginners.



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