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Why cloud architecture matters: The advantages of multi-instance vs. multi-tenant

By Allan Leinwand, CTO, ServiceNow | Aug. 26, 2016
Clouds that use a multi-instance architecture can better minimize the impact of an outage

With its inherent data isolation and multiple availability issues, multi-tenancy is a legacy cloud computing architecture that will not stand the test of time.

The multi-instance cloud architecture is not built on large centralized database software and infrastructure. Instead, it allocates a unique database process to each customer. This prevents data commingling, simplifies maintenance, and makes delivering upgrades and resolving issues much easier because it can be done on a one-on-one basis. It also provides safeguards against centralized hardware failures and other unexpected outages across multiple customers at the same time that a multi-tenant system cannot.

The most advanced multi-instance cloud providers are able to replicate application logic and database for each customer instance between two paired and geographically diverse data centers. Data replication can be done in near real-time with each side of the paired data centers fully operational and active. The use of orchestration and automation technology can quickly move customer instances between these replicated data center pairs. This architecture is deployed on a customer-by-customer basis thus eliminating the need for a disaster-recovery site – in a multi-instance cloud built in this manner you have two paired locations that are both always active.

It’s important to emphasize that multi-instance is not the same as single-tenant, where the cloud provider actually deploys separate hardware and software stacks for each customer. Like muti-tenant, there is some sharing of infrastructure pieces, such as network architecture, load balancers and common network components. But these are often segmented into distinct zones so that the failure of one or more devices does not affect a large set of customers.

Choosing an enterprise cloud platform is a lot like choosing a place to live. You could move into an apartment or condo building with a bunch of other people, or into a single-family house. At first, apartment living may seem like the more convenient and cost-effective option. You pay the landlord rent every month, relieving you of the responsibilities for on-going maintenance and upkeep. But you will soon discover that freedom is actually a collection of restrictions that prevent you from making any customizations. And a fire that breaks out in a single apartment is always a threat to destroy the entire building.

The multi-instance architecture provides the benefits of moving to a house. It follows the same approach enterprises use to run their mission-critical applications – with data isolated, a fully replicated environment that provides extremely high availability, and upgrades on a schedule it sets. In short, cloud architecture matters because it’s what enables a vendor to be highly available and to handle a sudden calamity - or not.


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