Multi-tenancy in the cloud: Why it matters

Computerworld -

Whether an IT organization is going with public or private clouds, it's important to understand the nuances of multi-tenant architecture. For public clouds, IT managers need to understand the degree of multi-tenancy supported by whichever vendor they are looking at. For private clouds, the entire responsibility of designing a multi-tenant architecture rests with the IT managers.

Enterprise cloud adoption has gone beyond the levels of intellectual pursuits and casual experimentation. An analysis by IDC shows that $17 billion of the $359 billion of worldwide IT spending for 2009 could be attributed to cloud computing. Two-thirds of Baseline magazine's survey participants plan to expand their use of public clouds.

None of that is to say that there aren't nagging issues, including but not limited to how different enterprise workloads match up against different types of clouds and responsible ways to plan and implement the necessary migrations.

Different IT workloads can be distributed differently across public and private clouds.
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Based on the characteristics of the workload, cloud adoption will swing between public and private clouds. Large enterprises have requirements that will force them to strike a balance between the two clouds for their workloads. This is different for small-to-medium businesses (SMBs) and start-ups, which might have a strong business case for wanting to use public clouds for almost all of their workloads. But in the end, their respective preferences will not be as much about the size of the organization as they are about the nature of their IT workloads.

Besides appropriate workload distribution, architectural considerations are also key. Multi-tenancy is one such architectural consideration, and understanding multi-tenancy is a critical first step towards broader IT cloud adoption.

Due to the early traction seen in public clouds -- where multiple enterprises end up being co-tenants -- "multi-tenancy" is wrongly used as a synonym for "multi-enterprise." But they are very different concepts. Also, the granularity of tenancy is established at the application level, not at the level of an individual user or entire enterprise.

Multi-tenancy defined

A tenant is any application -- either inside or outside the enterprise -- that needs its own secure and exclusive virtual computing environment. This environment can encompass all or some select layers of enterprise architecture, from storage to user interface. All interactive applications (or tenants) have to be multi-user in nature.

A departmental application that processes sensitive financial data within the private cloud of an enterprise is as much a "tenant" as a global marketing application that publishes product catalogs on a public cloud. They both have the same tenancy requirements, regardless of the fact that one has internal co-tenants and the other has external.