When buying a hard drive, there are three important factors to consider: capacity, rotation speed, and cache. All these elements play a role in how fast you can open, edit, and save your digital video.

Capacity is straightforward?the higher the number, the more storage space you have. I should mention here that you'll never get the full amount of space promised on the box. The reason is boring and technical, but as a rule of thumb, for every 100 GB your hard drive says it has, you'll get 93 GB of usable space.
 
Rotation speed?the number of times that a hard drive spins around per minute (much like a tire on a car): 5400 revolutions per minute (RPM) is standard, and 7200 RPM is what you'll see on high-performance drives consumer drives. On servers the drives can spin as fast as 15,000 RPM, but those drives are very expensive. For video work, and indeed for a faster performing computer in general, 7200 RPM is the best choice. That's not to say that if you have a 5400 RPM hard drive you can't work with digital video, but if you're buying a new hard drive I strongly recommend a 7200 RPM drive. Once you start opening and saving gigabytes of data, you'll appreciate the extra speed boost.
 
Cache size?cache on a hard drive is much like RAM on your computer. The cache acts as a temporary storage location for the data, and since the cache can respond much more quickly than the hard drive itself (nanoseconds instead of milliseconds), the more cache a drive has the better overall performance it will give. Most hard drives have 2 or 4 MB of cache?the Special Edition Western Digital drives and Matrox DiamondMax Plus 9 both have 8 MB of cache, which makes them top performers. I only buy drives with 8 MB of cache for this reason.  

There's another class of hard drive called a "SCSI drive" (pronounced "skuzzy") that you might hear mentioned when looking for a new hard drive. SCSI (Small Computer System Interface) hard drives offer some performance advantages over most standard hard drives, but SCSI hard drives are vastly more expensive, offer less storage space for your money, and require special know-how to configure on a PC. SCSI drives are very popular in the server world and high-end workstations, but for you and me, they're too expensive and too complex. And the good news is, a high-speed SCSI drive benchmarks roughly the same as a modern high-end consumer drive, so there's no reason to take on the expense of a SCSI drive.

Last update: 06:47 PM Saturday, December 9, 2006