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Maximum vs. Sustained Performance: What's the Difference?

by Matthew Mister, on Jun 25, 2019 3:29:33 PM

 

Maximum vs. Sustained Performance (2)

What are Read & Write Speeds?

When you are looking for any type of storage product you have most likely seen Read & Write speeds somewhere nearby. These are typically two numbers with some measurement of data per second next to it. But what do they actually mean?

Read/ Write speeds are a measurement of the performance on storage devices.  The read speed is a measurement of how long it takes to open a file on a device while a write speed is the exact opposite, measuring how long it takes to save something to a storage device.

Maximum vs. Sustained Performance

Within read/write speeds are two different measurements, these are maximum and sustained performance. These performance measurements give some idea into the stability and predictability of your media playback performance. 

So what's the difference between maximum and sustained performance?

  • Maximum performance: This is the highest speed the drive can run for a short period of time. This number may can get pretty high but the issue is that it is unsustainable. Let's compare this to an exotic sports car on a track, for example the top speed of a Lamborghini Huracan is 202 MPH so the driver can hit some insane speeds, but you can only maintain that speed for the length of a quick drag race before you start to blow the engine. 
  • Sustained Performance: This is a more predictable measurement, sustained performance gives you an idea of the average speed a drive will run over a longer period of time. If we go back to the Lamborghini example this would be similar to the average speed of the car over the duration of the race which will be slower for the sake of safety and longevity of the engine. Your sustained speed is what would win you a race like the 24 Hours of Le Mans.

How to identify maximum vs. sustained specs?

When you are searching for shared storage here are a few questions to ask yourself in order to tell whether you are looking at a sustained or a maximum performance spec. 

  1. Does the speed sound reasonable?: Various storage vendors have different ways of labeling their spec sheets. Some will only show you the maximum performance because it looks great on paper. Who wouldn't get excited about seeing a performance spec of over 4,000 MB/s? The issue is that across the storage industry the average sustained speeds run around 1,000-1,200 MB/s. So while, maximum drive speeds that look like Usain Bolt's sprint speed are exciting, your true sustained performance will probably be closer to a NFL lineman's speed.  
  2. How is it labeled?: When you are looking at a spec sheet, pay close attention to how the performance speeds are labeled. If you see something that says "sustained" or "streaming" speeds you are probably looking at the number you can rely on for running your daily business.  Many video focused vendors will also report these as "Stream Counts".  For a hard drive based system these will generally be in the 1,000-1,200 MB/s range with 8 drives and a 1,500-2,000 range with 16 drives.

Remember to keep in mind that while maximum speeds look and sound great, sustained speeds are the reliable measurement to base your operations around.

Can you improve read/write speeds?

The simple answer to this is yes, but you need to realize that this is only for a quick burst. You can add some things like Flash Storage or caching to move small files at a ridiculously fast speed, but if you try to maintain that over a larger file transfer you will never be able to sustain it and can risk blowing out your cache rather quickly.

Conclusion

There's a saying in golf that says "Drive for show, putt for dough", crushing the ball down the middle of the fairway may impress your playing group but if your putting is inconsistent you'll never win a tournament.

In the world of storage maximum performance is all about flash and impressive numbers, but sustained performance is what you can rely on everyday to keep your team up and running and hopefully raking in the dough!

Topics:NASpost productionshared storage

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