Virtualization
The costs of redesigning applications for multitenancy can be significant, especially for software vendors who continue to offer an on-premise single tenant version of their product. They end up being forced to support two distinct products with all the resulting costs.
An increasingly viable alternative route to multitenancy that eliminates the need for significant architectural change is to use virtualization technology to host multiple isolated instances of an application on one or more servers. Indeed, when applications are repackaged as virtual appliances the same appliance image can be deployed in ISV hosted, on-premise or trusted-third party locations and even migrated from one deployment site to another over time.
Read more about this topic: Multitenancy