Enterprise applications Toolkit

Posted by admin on March 6, 2010 under Help, Tutorials | Be the First to Comment

Multi-tenant is not virtualisation

I would take issue with the suggestion that multi-tenant applications means “multiple instances of the same package that can be executed on the same machine”; that’s virtualisation, and doesn’t require any particular magic at all. However it is grossly inefficient from an operational viewpoint – it means if I have 1000 customers for my cloud-based Exchange service (e.g.) I have to separately manage 1000 instances of Exchange.

A true multi-tenant application is a *single* instance application, albeit horizontally scalable on a massive scale, which is aware that there are multiple distinct entities using it and which is able to create very robust chinese walls between them, as well as effectively manage their resource utilisation. From the customer’s perspective it’s the same as virtualisation, insofar as it appears to him that he has exclusive use of the application instance, but from the service provider’s perspective it scales much much better. There’s only a single instance to manage, and I don’t have to worry about how to distribute resources amongst the various instances. When I add more capacity its available to be shared by all customers (subject to whatever QoS policy I may apply to individual customers). These aspects are critical for keeping the costs down.