Thanks for your comments. I’ll probably devote an entire blog entry to this topic soon. However, I can offer a little insight right now. By “multi-instance” I assume you are referring to an architecture where the same (or similar) schema is used with multiple instances of a database? In other words, each customer has its own database.

In my opinion, multi-tenant applications hold an advantage over multi-instance applications in the following ways:

1. You only have to upgrade a single database and code set
2. Data aggregation, data mining, and trend analysis are simplified if all customer data lies in a single database (data needs to be treated by vendors as an extremely valuable asset – more on this later)
3. Cheaper to host and maintain

I would not consider a multi-instance architecture SaaS because it’s not multi-tenant. You see, with a multi-tenant application you actually store all of your customers’ data in the same tables but you “attach” the data to each customer via a Customer ID or another identifier. In a multi-instance architecture you don’t need to have a Customer ID at all. While this certainly simplifies development, you lose all of your multi-tenancy benefits. Multi-tenancy DEFINES SaaS and is, in fact, the only real differentiator. Everything else is just a web application.

Question, how do you differentiate between a multitenant and a multi-instance architecture implementation and in your opinion is this considered a software as a service (SaaS) implementation, and why. Now this is not an easy nor simple question to respond to, I am interested in your thoughts around this topic. I look forward to hearing from you soon, and if interested, I have provided my Linkedin.com profile for your review, I look forward to your future postings and would enjoy an opportunity to discuss.

Kind regards,
Harold
972-464-1038
HaroldCHeardJr@Gmail.com

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