Hard Drive Buying Guide

If there's one thing we always need more of in a computer, it's disk space. Whether you just bought Windows Vista and it takes up more space, you listen to more music, or just just download too much illegal stuff, sooner or later you're going to run out of things to delete, and you'll have to go out and buy a new hard drive. But what should you look for in a new drive? It's not just disk space. Obviously that's the most important thing, but there are other factors that contribute to how fast the hard drive is. Since the hard drive is usually the slowest part of any computer, it's a good idea to make sure your new drive is as fast as possible. Here are a few things to keep in mind when buying a new hard drive.

Disk space
We all know this one, but there's more to it. You'll probably notice while shopping that up to a certain size you get about the same value for every drive (so a 500GB hard drive costs twice what a 250GB hard drive costs, etc.). You shouldn't buy a drive that's just bigger than your old drive. Instead, depending on your budget, you should buy a drive with the best value you can find. So if you see a sale on a drive, and it would give you a better value than the one you were going to buy, get the one on sale, even if it's bigger than you really need. In the end, you'll need that much space anyway, so if you're getting a deal you may as well.

Interface
Make sure your drive will plug into your computer. If you are buying an external hard drive, USB is the best option. FireWire is a faster interface, but some computers don't have a FireWire port, so be careful. If you are buying an internal hard drive, you need to know whether you need an IDE or an SATA hard drive. SATA is clearly the winner: it has faster transfer rates, you don't have to share the bandwidth of one channel between two drives, and the cables are a lot smaller, so you have less clutter inside the computer. But make sure you have available SATA ports first.

Spindle speed
The spindle speed is the speed at which the disk itself rotates. The faster the disk is spinning, the more chances the drive has to pick up a particular piece of data from it. Faster spindle speeds give you faster access times (the average time it takes to find a particular piece of data) as well as faster transfer rates (the rate at which large amounts of data are accessed from or written to the disk).

Typically all desktop hard drives are 7,200RPM drives, but they come with other speeds as well. Western Digital's Raptor series of hard drives run at 10,000RPM, which gives you a significant performance increase, but at a high cost. Benchmarks vary, but the Raptor drives could give you a 25-50% performance boost in certain applications.

Cache size
Usually this is prominently displayed on the hard drive box, as it's one of the important things. When certain data is accessed frequently, the drive puts it into a special type of storage called "cache." The cache is very small compared to the size of the drive, but it's a lot faster reading data out of the cache than the drive itself. In rare cases, you might be able to move all of the data you need to the cache and turn off the disk altogether (your iPod does this sometimes to save batteries). So the bigger the cache, the more performance it will provide. The typical internal drive today will have either an 8MB or a 16MB cache. Obviously, go for a drive with more cache. However, this is probably not something worth paying a lot of extra money for.

There are plenty of other specifications you'll find either on the box or on a company's website, but most of them you don't need to worry about. If you're concerned about noise, websites will usually show you a noise rating. Noise is usually measured in bels or decibels (1 bel = 10 decibels), where an increase of 1 bel or 10 decibels is a tenfold increase in noise. Lower numbers, therefore, mean less noise.

So, the next time you go shopping for a hard drive, keep in mind that capacity isn't the only important thing. It's obviously the biggest thing, but when you're comparing two hard drives with the same storage space and the same price, you now know there are other factors to compare.