Measuring performance (in the modern server world) …

September 28, 2011

In days gone by measuring performance was easy – Mb/sec (megabytes per second) was all anyone was really interested in. However measuring performance this way is only suited to systems where you are pushing large amounts of data through the system, not for measuring database or cloud-computing type environments.

For database we measure performance in IOPs – I/O’s per second. This measures how quickly small amounts of data can be transferred to and from the storage subsystem – in general the amount of data may not add up to many Mb/sec at all, so this traditional measurement method has little bearing here.

Now many customers are fully aware of these two measurement systems – and certainly anyone who has sat through one of my boring presentations is aware of where and when to use these two measurement systems, but there’s a new kid on the block that’s proving a little tougher to nail down.

Latency.

What is latency? It’s basically the amount of time it takes for information to be delivered to an end user, generally in a web or cloud environment. This metric is measured in milliseconds and for many organisations is the difference between profit and loss, or life and death.

I recently sat through a presentation with one of the industry’s leading experts in measuring data, and working out what is important to a customer. In that presentation I saw some pretty amazing statistics regarding latency:

Amazon consider that an additional 100ms latency costs 1% in sales (and that’s a very, very large amount of money),¬†Google consider that an additional 500ms latency reduces page viewing by 20% (in other words people won’t wait).

Those are just a few of the amazing statistics that customers attribute to high latency. For most people, it’s a case of just getting sick of waiting for a page of information to turn up on their screens, but there are big dollars behind that frustration.

So how do we measure latency? That’s the 64-dollar question because it’s not easily, or sometimes even possible to measure at the server point. When you take into account there are a lot of network factors inbetween the server and the end user it adds up to a complex environment to measure.

IOPs don’t necessarily relate to latency. Having high IOPs doesn’t always relate to low latency – in fact it can be quite the opposite.

Sounds complicated doesn’t it – well yes, it is. Adaptec have a lot of years of experience in sorting out problems for customers – whether it be streaming data speeds, database IOPs or now cloud latency – seems our work is never finished. So the question is … what sort of data do you have in what sort of environment, and how do you measure the actual, real performance of that data?

Ciao
Neil

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