In a recent post, we covered single-tenant vs. multi-tenant cloud CRM and touched on the idea that there are degrees of multi-tenancy among cloud CRM applications and among cloud business apps in general.

It turns out that not all multi-tenant business applications are created equal. Some are more multi-tenant than others.  Some are on a single, shared database schema (or instance) across all customers, where as others run on a collection of schema.

Why does the degree of multi-tenancy matter to customers?  For one, it’s easier for a vendor to manage application performance and security across a smaller number of instances. Second, there are fewer mechanics involved in rolling out new releases when there are fewer instances.

How do you measure the degree of multi-tenancy in an application?  One observational measure is the number of instances. For a given application, the number of instances may come down to how scalable the back-end database is. Google’s BigTable database does not have any apparent limits to schema scalability as it pertains to Google Apps for Business.

Three Degrees of Cloud Multi-Tenancy

Multi-Tenancy With Planetary Scalability

Google Apps for Business seemingly runs on a single, large global instance. Whenever there’s a new release of Google Apps features, which happens frequently, every Google Apps customer on the planet gets the release simultaneously — with one, intentionally baked-in exception. Google has provided the option for each customer administrator to put their organization’s account on one of two release tracks — either the Rapid Release track or the Scheduled Release track.  The idea is that customers on the Scheduled Release track have more time to prepare and train their users.

Multi-Tenancy with Regional Scalability

Salesforce.com currently has sixteen global, production instances. There are twelve North American instances, two Asia-Pac instances and two EMEA instances.  While salesforce.com has achieved a high degree of scalability within a multi-tenant environment, due to the sheer number of customers, it has hit a natural limit — possibly due to the size limitation of even an Oracle database.

When salesforce.com issues a new release (three times a year), the release is rolled across the sixteen instances in relatively rapid succession.  With many new features in each seasonal release, sometimes the release of certain new features are staggered after the main release.

Multi-Tenancy with Server Scalability

Microsoft CRM Online is only multi-tenant on its application instances. Microsoft CRM was built on top of a stack, including SQL Server, that was originally designed for enterprise scalability, but not for regional or planetary scalability. Because of this, each customer has its own database instance.

What this means is that Microsoft has to be more creative (and possibly more conservative) in its approach to rolling out new releases since there’s a one to one relationship between customers and databases. Also, overall management of the cloud infrastructure from a performance and security perspective may be more resource intensive than it is for Google or salesforce.com.

Real World Implications of the Degree of Multi-Tenancy

While this all seems like back-end stuff, the business impacts can be real and noticeable.  The behind-the-scenes factors can play into how well a cloud application performs, its overall availability and how quickly the application is iterated.