While SaaS is sending shockwaves through the enterprise cloud, a battle rages behind the scenes. Pardon the drama, but it is more than necessary. For years, the special sauce in SaaS (News - Alert) and cloud architectures was multi-tenancy, but as Willie Nelson once said, “The Party’s Over.” Another party rages on, but this time multi-instance is the architecture buzz blitzing around the dance floor.
For clarification, multi-tenancy means there is an identical cloud resource available on demand to any customer of the service. The customer’s data is stored in a shared, usually encrypted database. A vendor can easily upgrade a service by updating a single copy of the code, and all customers enjoy the enhancements instantly.
Multi-instance (MI), on the other hand, is a different flavor of multi-tenancy. In a recent diginomica piece, Brian Sommer defines MI as, “A public cloud deployment of an application where each customer is using their own copy of the software and has their data stored in their own specific RDBMS.” This is ServiceNow’s (News - Alert) approach, where they are responsible for any updates, conversions or necessary maintenance to the software.
As a result of ServiceNow’s Architecture, customers have the freedom to choose when it’s time to upgrade. Each customer is kept within the latest couple of versions, and never misses out on new functionality. Where multi-tenant leverages encryption to protect data, the ServiceNow approach creates a protective layer by storing said data on a specific device. Another key differentiation is when there is a problem, only one customer is affected – not all.
Another advantage to leveraging the MI architecture is in data recovery and backup. Each ServiceNow customer can, as Sommer put it, “halt their instance, do backups, and recover their data to a known point in time. Their actions would not affect other customers.”
When all the chips fall and the dust settles, it would be naïve to think multi-tenancy would be entirely old hat, but it is hard to argue against the advantages of the MI architecture. The enterprise cloud is a complex cornucopia of options at times, so there is no true right and wrong. As long as your IT operations are in rhythm, you have the proper architecture in place.