Comparing the idea of Grid computing to the new Buzzword “Cloud Computing” shows that - while the basic idea is the same - there are major differences in the two concepts.
One difference is obviously the intended usage. Grid Computing was planned for (single) applications with high demand in processing power while the idea of Could Computing is using such a grid on an internet scale to balance the load of many applications running in parallel.
This requires virtualization in order to provide the sandbox for each application:
Virtual Appliances are ready-to-run software packages that are pre configured on a virtual OS (or multiple ones), delivering a quick and easy to use solution for a certain part of the business. In my eyes, this is very appealing to all kinds (and all sizes) of corporations that do not want to go through the hassle of installing a local IT and facing problems when their business is growing (or shrinking) fast…
The main differentiator to SaaS is the Multi-Instance vs. Multitenancy. The control over a SaaS delivered platform is limited, while a virtual appliance allows full control in the VM boundaries.
Let’s hope that the Open Virtual Machine Format (OVM) will establish a standard that allows to create portable VMs that can move form local IT to the Cloud (and back) if required.
VMWare already introduced a concept called “vApp” that allows to package a set of configured VMs that compose one application and are managed as a unit.
Interesting times ahead…