Director vs. Core Switch


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Time is money.

At any other time, it's an overused and ought-to-be-forgotten cliche. But today, it's perhaps the most poignant and understated one-liner in the business world. Never before has so much ridden on so little, and never before have companies placed such a huge price tag on every minute of every day.

Whether your business is e-commerce, financial services, healthcare, retail, or government, each second your business is running equates to incoming dollars. And, each second your business is halted by data unavailability means lost immediate and future revenue. Even running in a degraded mode can result in prospective customers looking elsewhere

In assessing a business's application requirements, the application's current and future cost of downtime must be determined, so the associated network can be designed to support the application's availability requirements. Generally, if the cost of downtime is deemed high, the need for high-availability solutions is justified.

According to the Association of Contingency Planners, the cost of downtime per hour in the financial services industry is $6.4 million per hour. That means it costs a user $1,777 for every second they can't access their data. When you look at it that way, it becomes much more evident that availability is the crucial element in the storage networking switch selection process. Relatively new to cost metrics, running at less than full volume can also cost thousands of dollars. Have you ever decided to try a different Web site if the one you are using is sluggish?

When each second of network downtime equates to thousands of lost dollars, companies deploying storage area networks (SANs) today are posed with two choices - Directors and core switches. Directors or core switches are essentially the heart of a company's data infrastructure, pumping vital information through an extensive and complicated network of cables, storage and servers. If that heart stops, your business flat-lines. Here are a few things to consider when deciding whether to deploy a Director or core switch as the heart of your company's storage network.

Director or Core Switch?
A Director is a large port count, high bandwidth fabric switch, designed to provide the highest availability and performance. Directors have fully redundant, hot swappable components that minimize downtime. In fact, availability is rated at 99.999 percent or 'five nines'. 99.999 percent equates to five minutes of downtime per year, the most that a company running applications such as brokerage, online transaction processing or telecom can afford. Also, single-stage Directors utilize a 'crossbar' architecture that enables all ports to simultaneously interconnect with each other without performance degradation. This capability of simultaneously interconnecting without performance impact is often referred to as 'non-blocking'. Directors are a mature technology that complement fabric switches and are used in about 96 percent of the world's largest data centers.

Core switches, on the other hand, are new to the market. While they offer high port counts, core switches lack many of the attributes that define Director-class products such as highest availability, un-compromised performance, mainframe FICON support and certain environmental advantages. A core switch is basically comprised of a 16-switch mesh. Although easier to develop, a core switch is plagued with the blocking and latency issues inherent to a mesh design.

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