The SaaS is described as software applications deployed as a hosted service and accessed over the Internet via a standard web browser. This can include basic IIS or Apache software, and this called a software service.
When dealing with the Software as a Service model , the end user subscribe to applications versus purchasing them for a period of time.
So this is related to the operating system and other software that you use to host your database and systems. And for sure you can use Open-E for creating your storage server and to store your database and other files. Also you can use virtual machine system to deal with Open-E DSS and to create many virtual servers.