What do you do when you need more storage in a hurry, but are either reluctant to open your computer and install a new drive or need the ability to move your files to another computer? The easiest way, by far, is to connect an external hard drive to your computer. There are a wide array of drives on the market and a striking number of them are video-ready. Let’s investigate the features that you need to look for when selecting a drive for video.
A hard drive’s capacity determines the amount of data (and thus the amount of video) that you can store on it. 20-40GB drives are entry-level drives for video, but they are inexpensive and reasonably easy to come by. 80-120GB drives may well be the most mainstream and are not much more expensive than most entry-level drives. Staggeringly large drives (i.e. 200GB or larger) are out there, but they can be rather pricey. If you need to store a lot of video, these are the drives you want. Besides, calculate the price per GB and the larger drives are often the best deal.
Admittedly not quite as relevant a figure as it once was (thanks at least in part to the increasingly high densities found on today’s hard drives), spindle speed is still an important consideration. We’d recommend 7,200 rpm drives for DV video. Drives with higher spindle speeds tend to have faster seek times and can deliver higher throughput rates. However, reliability becomes a concern with extremely high spindle speeds (e.g. 10,000 or even 15,000 rpm) generating more heat and more head movement. Ultimately, this means more wear on the mechanism. 15,000-rpm drives are not necessary for DV production work and are actually designed primarily for server applications anyhow. In any case, don’t forget to make regular backups of your important files.
Sustained Data Transfer Rate
Sustained transfer rate is one of the more important characteristics to consider when purchasing a hard drive for video needs. The sustained data transfer rate refers to the speed at which data can be continuously moved onto or off of the hard drive (in contrast to the burst transfer rate, which is meaningless for large video files). Generally speaking, almost all USB 2.0 and FireWire drives can move data fast enough to handle DV, but more speed is better, providing a margin of safety that will help to ensure that no frames will be dropped when dealing with video in real time.
The drive’s interface determines the types of computers you can connect the drive to. Many drives use both USB 2.0 and FireWire ports, giving you the versatility to connect the drive to a wider array of computers. Either interface is more than fast enough for DV production. Our only caution is to make sure your computer has the right connection before you buy the drive. For example, older Macs do not have USB 2.0 ports, but they all have FireWire.
Access time is the amount of time, measured in milliseconds, that it takes the drive to locate a specific piece of information on the disk. Access times have decreased gradually over the years, but appear to be leveling out. While each access is tiny, added together, they can affect the performance numbers of the drive. Access time is not as important for video, where a single millisecond access may be all that is required for a single huge transfer of data.
Number of Platters
The number of platters a drive has corresponds to the density of the data at which the drive stores data. Drives with fewer platters are simpler to manufacture, but to store larger quantities of data on them, manufacturers must use some sophisticated storage methods, including advanced head designs and data encoding schemes. As a benefit to the end-user, drives with fewer platters are usually slightly quieter and generate somewhat less heat.
New drives include a buffer of solid-state memory, generally 2MB, but often as high as 8MB. The buffer accelerates read operations and provides a margin of security.
Not all external hard drives have power switches. Some are bus-powered, meaning that when you connect them to a FireWire or USB 2.0 interface, they will spin up and make themselves available to the computer without the need to plug them into the wall. Drives that use an AC adapter may stay on all of the time, even when your computer is off. A power switch would allow you to save some energy and may even save some wear and tear on the drive.
There you have it: a quick and dirty overview of some of the most important features to consider when shopping for an external hard drive. You can never have enough hard disk space, so when it’s time to add some storage to your system, an external hard drive is, without question, one of the best and easiest upgrade you can make.
Charles Fulton is an Associate Editor for Videomaker Magazine.