My two-cents worth: There is an Error Recovery problem in SCSI-land.
A serious one. Certain failures would cause the system to freeze.
Most HBA drivers do not recover very grwcefuly from hardware failures.
The SCSI tape code locks up devices upon failure and refuses to release
the calling process for what appears to be eternity.
Indeed there is. I'm working on tracking a few of these problems down right
now...
Leonard