PC Hardware in a Nutshell, Second Edition

ATA Versus SCSI

Relative to ATA, SCSI has the following advantages:

Performance

ATA drives simply cannot compare to SCSI drives in performance under load. In our real-world testing, the slowest SCSI drives we used were faster than the fastest ATA drives, particularly under Windows NT/2000/XP, Linux, and other multitasking operating systems. This held true across the board, even when we tested an elderly, midrange Seagate SCSI drive against the fastest of the current ATA drives. Although ATA may match SCSI under light load, when disk activity starts to climb SCSI is simply faster. Don’t let anyone convince you otherwise.

Tip

To verify our impression of SCSI versus ATA, we did an experiment. Barbara’s main workstation uses a 7,200 RPM SCSI Seagate Barracuda drive. We built an identical system, but substituted a 7,200 RPM Seagate Barracuda ATA IV drive. For normal operations, performance of the two PCs was indistinguishable.

We then started an XCOPY operation that streamed gigabytes of data comprising hundreds of directories and thousands of files from a third system across our 100BaseT network to the hard drive of the ATA system. While that data was being copied, the ATA system was nearly unusable. Loading Word from the hard drive took literally a full minute, and opening a large document took even longer.

We then repeated the experiment, but this time to Barbara’s SCSI Barracuda. The drive banged away, certainly, but we were able to load programs and run things normally with very little ...