Hi Ray, One of my client ask about the security issue. ie, can any one access their database? will our company access their data? etc... They are mainly pointing out the security issue. Please refer a clear answer that i can share with my clients.

In both cases the customer (who purchases the cloud computing server) has 100% control (root access) to the machine. This means it has the same security problems as any machine of their own. Amazon and Rackspace cannot access the machine unless the customer chooses to give them access. Every port on the machine can be opened or closed to every protocol. You have the same access as if it was your own machine, and can open it up or close it down in the same way as your own machine.

Would it be better to have multiple databases in a single running instance or to make an instance per customer? Are there performance or capacity issues for each option?