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Gigabytes per second or Giga-buts per second?

March 24, 2013 by Steve Modica

Steve ModicaEvery year as NAB approaches, the marketing once again begins.  Oh the marketing….

As NAB approaches, I’d like to take a moment to remind people in the market for storage that Gigabytes/second is not what makes video play smoothly.

Vendors with no Computer Engineers on staff will pull together monstrous conglomerations of SSDs and RAID cards, run a few benchmarks (probably four or five different ones until they find one they like) and then claim they’ve hit some huge number of Gigabytes per second.

Small Tree has been supporting Server based video editing longer than anyone in the market.  We were supporting Avid when they used SGI’s 10 years ago (and they were SGI’s largest customer). We know how things work. We helped develop them.

Playing video requires a RAID configuration that can handle multiple, clocked streams. Benchmarks on the other hand, tend to use a single stream, reading sequentially as fast as they can.

What’s the difference you ask? Well, in the sequential case, the RAID controller gets to use lots of tricks to avoid the hard work of seeking around disks and reordering commands.  The next block to be read is probably the next block, so things like “read ahead” work wonderfully. Don’t just read the next 128k, read the next 1MB! It’ll all be read next anyhow.  It makes it very easy for sequential benchmarks to look good. In the Supercomputing world, meaningless TeraFLOP marketing numbers were referred to as “MachoFLOPS”. We knew they meant nothing when vendors could spin assembly instructions in a tight loop and claim 1.5PetaFLOPS.

Small Tree’s testing and development involves looking carefully at how the Video Editing Programs themselves read so we can carefully mimic that traffic during testing. This lets us be sure our equipment doesn’t rely on sequential tricks to deliver real, multi-stream performance.

So when you walk up to a vendor at NAB and they start telling you about their MachoGigabytes per second, make sure you ask them about their sustained latency numbers. Small Tree knows all about latency and we back it up, every day with our products.


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