The Divisive Issue of Multitenancy

Multitenancy is a characteristic of SaaS, and sometimes PaaS, where numerous customers run the same application, sharing the same equipment and software, but each accesses only his or her data. Perhaps the best known example is the Google Apps Premier Edition, a SaaS service (www.google.com/apps/intl/en/business/index.html). More than two million unique enterprises, each operating under its own domain name, share the same Google infrastructure and cloud, which altogether supports tens of millions of individual users.

Some argue that multitenancy is the conditio sine qua non (a mandatory condition) for �true� cloud computing; certainly, it promises the greatest cost savings. Of course, the cost savings can be offset by the difficulty of scaling an application developed to support a single user to securely support many, as well as the problems of scaling from a single instance to many instances (a bigger, faster server can only take you so far) as the demand grows. In addition, the actual development of a multitenancy system is somewhat more complex, and the testing necessary for security needs to be more stringent.

On the other hand, multitenancy simplifies the release management process. In a traditional release management process, packages containing code and database changes have to be distributed to individual client desktop and/or server machines and individually installed. With browser accessed applications using the multitenant model, the package typically only needs to be installed on a single server and is automatically propagated to other server instances. This greatly simplifies the release management process. (In essence, this is the great-grandchild of service bureaus that handle applications such as payroll on behalf of many different customers).

Source of Information :  Implementing and Developing Cloud Computing Applications 2011