Architectural Multi-tenancy

Almost every definition of cloud, amongst the myriad definitions that exist, include the notion of multi-tenancy, a.k.a. the ability to isolate customer-specific traffic, data, and configuration of resources using the same software and interfaces. In the case of SaaS (Software as a Service) multi-tenancy is almost always achieved via a database and configuration, with isolation provided at the application layer. This form of multi-tenancy is the easiest to implement and is a well-understood model of isolation.

In the case of IaaS (Infrastructure as a Service) this level of isolation is primarily achieved through server virtualization and configuration, but generally does not yet extend throughout the datacenter to resources other than compute or storage. This means the network components do not easily support the notion of multi-tenancy. This is because the infrastructure itself is only somewhat multi-tenant capable, with varying degrees of isolation and provisioning of resources possible. load balancing solutions, for example, support multi-tenancy inherently through virtualization of applications, i.e. Virtual IP Addresses or Virtual Servers, but that multi-tenancy does not go as “deep” as some might like or require. This model does support configuration-based multi-tenancy because each Virtual Server can have its own load balancing profiles and peculiar configuration, but generally speaking it does not support the assignment of CPU and memory resources at the Virtual Server layer.

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