One of the secrets of cloud computing is that cloud software reflects a new architecture that best exploits the clustered resources around it. It exploits them in such a way that one instance of the software potentially can serve hundreds or thousands of users, and a handful of instances can serve hundreds of thousands.
Software as a service works because the multi-tenant application is unlike the linear logic of the serial applications that have gone before. Instead of each section of the application being retrieved from disk as the application marches through its prescribed logic, the multi-tenant application in most cases already resides in memory.
Different parts of it can be called at different times by different users, with those needing similar functions being ganged together by the application's middleware and managed as one call and application response. Thus, where an application served one end user before or a mere handful, now it serves multitudes, juggling a variety of calls and satisfying end users of different stripes without breathing hard or breaking into a sweat.
The world of enterprise IT was uncertain that multi-tenant applications could be counted on until Salesforce.com came along and Marc Benioff proclaimed the death of software, the old software as we knew it behind enterprise walls. Legacy systems did not die in the face of software as a service, but Salesforce CTO Parker Harris' cloud application was born and thrived.Put computing resources at your fingertips on-demand and only for the period of time required. Securing The Cloud In Fed Agencies
We are now witnessing the software that surrounds an application and provides it with its multi-server power undergoing its own phase of cloud-enablement.
It's fine that Web servers, Web portals, identity management servers, load balancers and application servers all bring their specific functions to the party for a cloud application. But embedded in each type is a lot of functionality that's also contained in the others. What if, instead of repeating that function each time a new server is created, you could generate one version that sat in the center of the middleware and provided the same capability to all. Instead of needing security characteristics embedded in each server, you could create the security function once, then let each server call on it from a central source, when needed.
That's how it would be done in an era of cloud software architecture: one source serving many, and one source, propagated across a small server cluster serving many more. Such a middleware design would leverage carefully created functions. A centralized function, sitting at the core of a system, would give the software "elasticity" inside the cloud, just as cloud hardware has an automated ability to expand or contract to meet demand from those outside it.
In the June 3 InformationWeek story on WS02, a centralized middleware function, much like that described above,is found in WSO2's core Carbon 3.0 product. In a private cloud implementation of Carbon 3.0, the other middleware acts as stripped down modules of Web serving, application serving or identity management serving, while plugged into the core system. The Carbon core captures any function that's shared across the middleware suite and makes it available when any of the specialized server modules say it's needed.
This is a cloud-centric design. It implements that still little articulated principle of cloud software that any software resource will be instantiated just once but used perhaps thousands of times a minute or even every few seconds. Having created Carbon 3.0, WSO2 was in a strong position to add portal-based self-provisioning and deployment, a service catalogue, chargeback and other cloud enabling extensions that give its middleware more of the characteristics that we've come to identify as essential to automated, cloud-like operations. These have been dubbed the Stratos part of the WSO2 product line. But they would have little meaning or impact if they didn't have a Carbon core.
Carbon represents a next phase of middleware, an essential concentration of shared function combined with central application management intelligence, two ingredients of future cloud implementations.SOURCE : http://www.informationweek.com/cloud-computing/blog/archives/2010/06/a>