Gordon Laing

PC performance can be a funny thing. Many systems race through general tasks, making you question the need for ever faster parts, and then grind to such an agonising crawl on others that you wander off and fix yourself a drink, or even a meal.

One of the toughest modern applications is video editing, which gives your entire system a workout. Processors, memory and even graphics chipsets often max out when rendering effects and converting formats, while hard disks are hammered in capturing and editing clips or writing the finished project.

Over the years I’ve found myself doing more and more video editing. It’s now by far the most demanding task for my PC. I can live with the delays of a final render as it’s something you can walk away from. But unresponsiveness while editing can be infuriating. As you drag the timeline slider back and forth you want to see your frame rendered on-screen in real-time, as any delays make precise edits and nudging back and forth very difficult.

While most hard disks deliver smooth performance with a single video stream, they have problems reading two or more simultaneously. Transitions, voiceovers and picture-in-picture effects all involve the I/O system reading multiple files from different areas of your hard disk at the same time – and with video we’re talking hefty sizes at high bit-rates.

To improve I/O performance, serious video editors exploit Raid, which uses two or more disks working together. Raid 0 is the most popular for video as it stripes data across multiple disks to improve speed. Should one disk fail, you lose the entire array, so Raid 0 is only suitable as a temporary work area before shifting finished projects to a safer location.

In contrast, Raid 1 mirrors data across pairs of disks, so if one fails, the other seamlessly takes over. However, you only get to use half your total storage space.

It was these reasons which drew me to Raid 5, which uses three or more disks to protect against failure, but makes more efficient use of space – you only lose one disk’s worth. The downside to Raid 5 is poor write speeds, but a hardware accelerated controller can do wonders. Which is how I ended up with a triplet of 300GB disks hosted as a Raid 5 array on an accelerated Promise controller.

I used it to store my documents, emails and photos, but over time it also became the working area for video projects. Standard benchmarks like HD Tach showed that while it wasn’t as quick as Raid 0, it still delivered better performance than a single disk.

I’d been happy with this arrangement, but when recently upgrading with three 500GB drives, I took the opportunity to run additional tests to see if Raid 5 was still my best bet. I still used HD Tach for pure benchmarks, but also copied the files from my latest video project onto each test array and checked responsiveness and final render times.

As before, HD Tach confirmed Raid 0 as the fastest overall, although accelerated Raid 5 ranked fairly close in some respects. But Raid 0 was significantly better when using Adobe’s Premiere video-editing software: almost a third faster in render time, and giving a much snappier response when editing. This is what I was really after, but it put me in a quandary: should I stick with the good all-round Raid 5, or trade it in for the extra speed but extra risk of Raid 0?

In the end I decided to go for the best of both worlds and built two arrays: the new disks in a reliable Raid 5 volume, and the older ones reconfigured as a quick Raid 0 work area. I’m looking into a switch to power up only the Raid 0 array when required.

The important lesson in this process is that when upgrading or rebuilding, don’t rely solely on raw benchmarks or what’s worked for you in the past. Run tests with your most demanding current applications and latest files to see which configurations will perform best for you right now. This process ensured I got the best setup for my current requirements.

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