Cloud Computing, Virtualization, IaaS, PaaS and SaaS - Part 2

In part one of this post, I looked in to the question of why cloud computing is important. In this post, I will look into the question of what cloud computing is.

NIST's definition of cloud computing gives a useful model for deciding what is and is not a cloud deployment:
 "cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction."

But to understand what "the cloud" is really made up of, it helps to look at how cloud computing is packaged and sold.

• Infrastructure as a Service (IaaS)
• Platform as a Service (PaaS)
• Software as a Service (SaaS)

Infrastructure as a Service (Iaas)
In this cloud offering, the seller provisions virtualized compute, network and storage upon which the buyer installs his own operating system and software. This is most easily thought of as buying bare computers and storage onto which your own IT dept will put everything required for your specific uses.
A few major vendors who offer these products are: Amazon Web Services, RackSpace and AT&T Synaptic Hosting.

Virtualization software is key to making IaaS feasible. Without virtualization, physical hardware would need to be provisioned for each customer. This would make it prohibitively expensive to quickly provision, re-provision and scale resources to meet customer needs.
The major virtualization s/w vendors include VMWare (ESX), Microsoft (HyperV) and an open source virtualization solution Xen.

More on virtualization in another post.

Platform as a Service (Paas)
In the platform level cloud offering, the seller provisions some combination of operating system, middleware and runtime packages which enable the buyer to develop and run applications of their choosing. This can be thought of as buying access to services which enable programs to easily access the resources they need to run.
Vendors provide a variety of offerings in this space. A few major offerings are below:

• Google App Engine provides a number of runtime environments for web application developers.
• Amazon Simple Storage Service (S3) provides file based storage to any application which needs it while Amazon Elastic Block Store (EBS) provides block level storage for applications the need direct storage access (like DBs).
• Microsoft Azure provides access to a few runtime envrionments,  SQL DB services for applications which need DB services and the virtual network fabric required to link together multiple server's services.

Software as a Service (Saas)
In this level of cloud offering, the seller provides the buyer with access to end applications while hiding the infrastructure, middleware and runtime components. Pretty much every time you hear about a "web application" being offered by a company, you are seeing a SaaS product.
There are probably thousands of SaaS offerings available so covering any significant fraction of the space here is futile. But here are a few examples of SaaS offerings:

• Web email - from google, Yahoo, etc
• Office 365 and Google Apps - On line productivity apps for creating, accessing and collaborating with others on a variety of document types (word processing, presentations, spreadsheets, picture editing, etc).
• Sustainable Supply Chain (SSC) - Supply chain survey management for corporate social responsibility reporting from CSRware.
• Facebook and Google + - public social networking tools for keeping tabs on your friends around the world.
• Socialcast, Clearvale , Jive and Spigit -  Enterprise social networking tools for keeping abreast of news and status, smoothing workflow, fostering collaboration and spurring idea generation in a corporate context.

One additional consideration is which user base a cloud deployment is intended to serve. This leads to the ideas of: Private, Public and Hybrid Clouds

• Private cloud = services and (often hardware) are strictly for a single company's use. Frequently this implies that the company consuming the services will deploy the cloud services on hardware behind their corporate firewall.
• Public cloud = services are available for all users anywhere. Though users may need to pay for services... This is the context in which most people experience the cloud because of the heavy reliance start-ups offering SaaS products have on public cloud services.
• Hybrid cloud = multiple cloud systems connected in such a way as to allow programs and data to be easily moved between private to public clouds.