What specs to review before buying a hard drive

The speed of your hard disk is a major factor in your system’s overall performance as much as its capacity. After all, the faster it’s able to find data and transfer it, the quicker Windows will load, the faster your virtual memory (i.e. pagefile) will be, and the less time it will take to start applications and copy files.

Budget is usually the deciding factor when choosing a drive, but with a larger budget, people usually just opt for more capacity. If you want the best performance, though, consider these factors to be at least as important:

RPM (revolutions per minute)
This is the speed at which the disk spins; higher numbers are faster. Cheap drives spin at 5,400 RPM, but you shouldn’t settle for anything less than 7,200 RPM. If you’re serious about performance, get a more expensive (and harder to find) 10,000 RPM (10k) or 15,000 RPM (15k) drive.

Buffer (measured in megabytes)
The buffer is memory (RAM) installed in the drive’s circuitry that allows it to accept data from your computer faster than it is able to physically write to the disk surface, and to read data from the disk surface faster when your PC isn’t necessarily ready for it. A larger buffer is better; don’t settle for less than 8 megabytes.

MTBF (measured in hours)
Admins should take note of this factor. It doesn’t matter how fast a drive is if it dies on you. The higher the MTBF—Mean Time Between Failures—the more reliable the drive is supposed to be. Of course, this isn’t a guarantee, but rather merely an indicator of the market for which the drive was designed. Hard disks designed for servers tend to have much higher MTBF ratings than the low-end disks available on most computer-store shelves.

Aside from the specs, you’ll also need to consider the interface, the connector on the back of the drive that must match the drive controller and cable already in your PC.

Here are your harddisk interface choices:

SATA (a.k.a. Serial ATA)
For most Vista users, SATA is probably your best bet. It’s faster than IDE (next), supports hot-swapping (connecting and disconnecting while the PC is on), and is easier to hook up (no jumpers or ribbon cables). Look for a SATA 3.0 (also known as SATA II) drive with the NCQ (Native command queuing) feature for the best performance.

The main drawback is that SATA connectors are flimsy and easily broken, so if you’ll be hot-swapping your drives, consider instead eSATA (SATA with a stronger connector for external drives) or SCSI.

ATA (a.k.a. Parallel ATA or IDE)
This interface is now totally obsolete. Even if you have an older PC with only an IDE controller on the motherboard, it’s usually a better idea to get a SATA card ($20–$30) and a SATA drive than to invest in an older IDE drive. Consider IDE only if you have a laptop that just takes 2.5-inch IDE drives, or if you need to set up a dual-boot system with an older version of Windows that doesn’t support SATA.

SCSI/SAS
Ultra320 SCSI is still faster than SATA, and will likely be your only choice if you want a super-fast 15K RPM drive. But given that SCSI controllers are unreasonably expensive, as are SCSI drives, consider this option only if you absolutely need the fastest drive money can buy.