I did some rough speed tests comparing my Quantam Atlas V 9gig scsi hardrive with my Western Digital 80gig ultra ATA drive.
copying an 86 meg file three times from the Ramdisk to each drive:
Quantam Atlas V: 19.8 sec.
Western Digital ultra ATA: 16.7 sec.
*note both drives have a spindle speed of 7200 rpm but I think the difference comes from the ultra ATA Bus having a 32bit bus compared to the Symbios895 scsi 2 ultra using a 16bit bus. these timings are not perfectly accurate because I used a stopwatch. also I noticed that transfers to the atlas consumed about 31% cpu usage, while the same transfer on the Western Digital ATA used 77% cpu usage.
Next I should compare swapping a directory with many small(er) files.