I doubt the SCSI controller has DMA... if it is anything like the other macintoshes.
That would put a massive hurting on performance. Also don't forget that SCSI-1 is only 5Mbps and SCSI-2 is only 10Mbps theoretical max bandwidth... I woudln't be supprised if the drive maxes out at 500Kbps perhaps you could try a drive benchmark.
http://www.ikasu.net/lombard/hdd/scsi/20-500m/
500Kbps is roughly 60KBps... so perhaps a few random IOs are slowing down the drive access as well? Otherwise thats quite slow given those benchmarks which help put things in perspective.
That would put a massive hurting on performance. Also don't forget that SCSI-1 is only 5Mbps and SCSI-2 is only 10Mbps theoretical max bandwidth... I woudln't be supprised if the drive maxes out at 500Kbps perhaps you could try a drive benchmark.
http://www.ikasu.net/lombard/hdd/scsi/20-500m/
500Kbps is roughly 60KBps... so perhaps a few random IOs are slowing down the drive access as well? Otherwise thats quite slow given those benchmarks which help put things in perspective.