You might want to fix your twitter link (it’s currently twiiter).

Thanks for the catch! Done….

I agree. Doesn’t virtualization and the latest tools to automate provisioning, monitoring, management, code updates/syncs, testing and failover make the need for multi-tenancy moot? So what if its made up of separate stacks if it can scale, is highly available and can be efficiently and cost-effectively monitored and managed?

Jan – This gets to the core of the misconception that keeps providing nothing but confusion. The answer is – NO.

Some cloud hosting providers have some or parts of the tools you mention. Most are aimed at the infrastructure (hardware and networking) and common tools. Automation of updates to core functional tools like databases or interpreters can break applications in many unexpected ways because of version dependancies. Automated instance deployment is really nothing more than scripting for the most part.

And yes, any good web application should be made up in stacks – the display layer, the database layer, the logic tier or whatever your break down happens to be. But that doesn’t eliminate the need to update those layers when you make a change to them. Why would anyone want to update 1000 instances of one or more layers when they could update some much lower number – maybe 5 or 10 multitenant instances? And – if you have heavily customized individual instances to meet customer needs – how might those be impacted by an update? You will have to test each one to see.

And what about economies of scale? Putting aside maintenance overhead – will 1000 instances all with their separate threads run as efficiently as 10 multitenant instances? The simple answer is no – cloud hosting is not optimized that way.

And what about using the idea you are on the Internet and in a (by default) community of users under this application? Are there reasons why user communities might want to interact?

I know many providers want to jump on the “SaaS” marketing bandwagon and tout their offering as making it simple to build and deploy applications for vendors. Right now there are very few vendors who can rightly claim to have provided a transparent platform that provides scaling and multitenancy to a single tenant architecture. But those are platforms – not just cloud hosting providers. The ones that are good do have a level of “lock-in” as a risk but it is a trade off that can be evaluated within all business risks that SaaS vendors face.

“Most multitenant applications use individual database instances for every client”

I’m just curious, how do you know this? How many multitenant applications have you investigated to come to this conclusion?

As I mentioned in the article – this is an assertion by people putting forward the idea of single tenancy as a strategy for SaaS architecture. As I responded – many do use individual database instances but whether it is a majority or not is an unknown. I do know from talking to leading hosting providers in the field that it is a common problem.

I don’t believe it is a good strategy however – for the reasons I listed in the article.

Given the recent developments with both Ariba’s as well as Oracle’s entry into the SaaS or on-demand world, I wanted to see if you would be willing to be a guest on the PI Window on Business Blog Talk Radio Show (http://www.blogtalkradio.com/Jon-Hansen) to discuss the issue of single versus multi-tenancy relative to these latest developments.

Note: Here is the link to Part 1 of my 2 part series on the Oracle April 9th announcement: http://procureinsights.wordpress.com/2009/04/13/oracle-launches-sourcing-software-on-demand-as-life-imitates-art-so-too-does-business-imitate-politics-part-1/

Would you be available on either the 30th of April or the 21st of May?

Best Regards,

Jon