As The Hard Disc Spins (1) Print E-mail
Written by Michael Schuette   
Dec 06, 2003 at 11:35 PM

I: Internal Drive Performance

Hard disk drive technology has moved more and more into the center of attention of the IT industry. The original role of HDDs was meant to be a simple mass storage media with relatively little emphasis on performance; twenty years ago, this did suffice. With the internet evolving and servers becoming a powerful factor in the electronic fabric of data communication throughout the entire world, it soon became obvious that storage media were also the most prevalent bottleneck, thus, the need for increased performance.

Performance of hard disk drives is a rather touchy topic, depending on who one asks, one may get very different answers, based on the different criteria applied and the different benchmarks used. Buzz words like internal performance, seek latencies, media transfer rates, response times are being thrown around, burst speed and effective host transfer rates are held against those and last not least, the cache size matters.

This is the level of argumentation for a single drive, once the subject switches to RAID configurations, things are getting even more complicated. In addition, there are the standard benchmarks and then there are those advanced benchmarks like IOMeter, which by their mere use already qualify the testers as experts. Or not?

In this and the following articles we will first discuss HDD performance in general, then go about a few basic functional drive architecture parameters and finally discuss how certain benchmarks fit into the grand scheme. We will also show, which benchmarks, despite their popularity are either meaningless for the end user or else create a false impression of the drive's capabilities. There will be follow-up articles that will deal in greater detail with individual benchmarks.

What is HDD Performance Anyway?

Before addressing in detail the drive architecture and performance metrics, we need to look at what HDD performance really is. HDDs can be compared in many ways to either a Supermarket or else an elevator and we are going to use these two comparisons throughout the discussions of the different subjects at hand.

Let's start with the shopping list first. Anybody familiar with a supermarket will know that filling a shopping list can be a daunting task for a variety of reasons. The first reason is that the items on the list rarely are in any order that only vaguely reflects their arrangement throughout the supermarket. The second issue is that often enough, there are different choices to be made, one thing is on sale, the other one is not, there are different size containers at different unit prices and there is the ubiquitous get one get one free promotion. Finally, there is the task of getting to the checkout register with the least waiting in line, which is not necessarily the one with the shortest line.

In general, the best performing HDD would be one that manages to get the shopping done in the least amount of time and, at the same time, to get the best deal for the money. Does that sound like your average HDD? I bet it doesn't but that is really what modern drives are capable of.

Only as a sneak preview, this brings us to the inadequacies of the current HDD benchmarks that are concerned with burst transfers and sequential data transfers. The pictures painted by these benchmarks are equivalent to taking a stopwatch and having someone run through the supermarket as fast as he or she can with the additional task of grabbing one random item per row. In this case, racing through the aisles is equivalent to the sequential media transfers. The quickness of how fast those random goodies can be ripped from the shelves would be the burst transfer rate. Do those benchmarks characterize a good shopper? Or, by extension, a good HDD? I rest my case - and we'll talk about the elevator later



Last Updated ( Dec 07, 2009 at 03:34 PM )
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