Hallo, I have a small issue with the scsi...
I have two fast disks, ibm DCAS34330 and Seagate Barracuda (all 4gb) but I not able to have speed over 5mb/sec. Sysinfo show me 4,5mb/sec, scsispeed 5mb/sec at max.
I have active termination, short cable, jumper is at synchronous and I have Buster 11.
My config is: A3640 v3.1, 16mb, kick 3.1, wb3.1, net a2065, merlin 4mb. No ide devices.
Maybe the merlin use to much zorroIII bandwith?
Another problem: at normal use I not have problems, but if I go in the boot menu and exit.... I have the kick screen! I need to manual reset to start hdd load. Same problem with wb3.9 kickstart replacement: it load the kick replacement and reboot to kick screen... I need to reset to loading the workbench. Why?
Do you have the latest rev 7.0 roms for the 4091?
Are you using active termination?
the ibm drive is a bit slow at only 5400 rpm,looking at the data sheet its rated 40Mbps external transfer rate,and guess what...this is about 5MB/s

this drive is doing what it is supposed to.
The seagate barracuda(is this the one that sounds like a jet plane???) you dont give a model so i cant look it up, if its the 7200rpm version it should do a bit better i would think.
Things to check/try:
What filesystem are you using? FFS is slow, use SFS or PFS-AIO
Try the seagate alone if possible.
use active terminators.
try upgrading the roms if possible.
There could be contention with the merlin-those cards were known to be problematic,some even with the upgrades, you might take it out and try the tests.
Sometimes booting with a clean workbench 3x floppy and running the speed tests will give a clear true idea of speed.
Good luck and let us know what you find.