What is Multi-Tenancy and Why is it Important for Cloud Disaster Recovery?

By Zerto, on 21 June, 2012

A multi-tenant architecture is the key enabler for cloud service providers to create efficiencies which enable them to offer their services at an attractive price. There’s a lot of useful information online about the concept of multi-tenancy:

The NIST definition of could computing centers around the essential characteristics of all clouds, one of which is multi-tenant architecture – defined as the enabler for pooling of resources.  Another good definition can be found here: “Multitenancy Can Have a 16:1 Cost Advantage Over Single-Tenant”:

“Multi-tenancy is the ability to run multiple customers on a single software instance installed on multiple servers to increase resource utilization by allowing load balancing among tenants, and to reduce operational complexity and cost in managing the software to deliver the service. Tenants on a multitenant system can operate as though they have an instance of the software entirely to themselves which is completely secure and insulated from any impact by other tenants.”

This post, “Architecture Strategies for Catching the Long Tail,” supplies a good example of how multi-tenancy is being used:

“When a user at one company accesses customer information by using a CRM application service, the application instance that the user connects to may be accommodating users from dozens, or even hundreds, of other companies—all completely unbeknownst to any of the users. This requires an architecture that maximizes the sharing of resources across tenants, but that is still able to differentiate data belonging to different customers.”

A recent article in CloudTweaks, “Multi–Tenancy In The Cloud: Understanding Its Benefits,” explains that with multi-tenant architecture, multiple customers may be using an application with specialized customizations:

“Customers may have the ability to configure some parts of the application…although tenants are using the same building blocks in their configuration, the appearance or workflow of the application may be different for two tenants. Also, the Service Level Agreement (SLA) of each tenant can differ.”

Are multi-tenant architectures secure?

According to a recent study by Forrester Analyst John R. Rhymer, “Despite resource sharing, multitenancy will often improve security. Most current enterprise security models are perimeter-based, making you vulnerable to inside attacks. Multitenant services secure all assets at all times, since those within the main perimeter are all different clients. Leveraging a mix of dedicated resources and metadata map architectures, these services can deliver stronger security.”

I’ve heard multi-tenancy compared to tenants in an apartment building who may share much of the building infrastructure – like pipes – but do not actually share the resources – like the water tenants use to wash their dishes. Simplistic, but works for me!  Phil Wainewright, in an article on ZDNet, continues the analogy. “In theory, a single house with a fence around it is much more secure than an apartment in a block shared with many other households. In practice, the householders in the apartment block will pool the cost of having a porter on duty 24×7 to control access to the building and monitor security. Most multi-tenant systems are operated to much higher security standards than standalone systems.

Let’s Summarize –

Multi-tenant architectures allow cloud service providers to offer services which:

  • “are completely secure and insulated from any impact by other tenants.”
  • “maximize the sharing of resources across tenants, but still able to differentiate data belonging to different customers.”
  • “use the same building blocks [but] the appearance or workflow of the application may be different for two tenants.”
  • “despite resource sharing…often improves security.”

What happens without multi-tenancy?

Without multi-tenancy, duplicate instances or infrastructures are required, complexity of the environment is increased significantly and the benefits expected in the cloud – flexibility, ability to scale and adaptability and particularly cost-efficiency – are reduced.

Multi-tenant cloud disaster recovery

Replication can add another layer of complexity to cloud offerings, especially when most DR solutions are not designed specifically for the cloud.  As a result, duplicate servers, appliances and networks are required in the environment and the ability of the cloud provider to pool replication resources is undermined. Leveraging cloud infrastructure to gain economies of scale helps the cloud service provider keep costs in line and offer disaster recovery services to customers at an attractive price. This is compromised without true multi-tenancy. How? Stay tuned for next week’s continuation post; multi-tenancy in Cloud DR architecture –  why you can’t have real cloud DR without it.

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