Disks Hang Under 2.0.2 SCSI

neese at adaptex.UUCP neese at adaptex.UUCP
Fri Dec 15 10:38:00 AEST 1989

>We have had the same failure here under similiar conditions.  Configuration
>here is an Adaptec host adaptor and 2 380 mb Newbury data drives.  
>Our problem seemed to manifest itself mostly under pathalogical conditions,
>such as when a bad block is discovered.  I've also seen it when I've been
>running a script similiar to yours designed to hammer a new hard disk before
>putting it into service.
>The external symptoms are as you note PLUS I notice that the activity LED
>on the Adaptec board is stuck on AND the activity LED on one of the drives
>is on continously.
>We now have a bit more data in that it occurs on two totally different
>drive types.
>Without any investigation other than external observation, I suspect that the 
>problem has to do with either a buffer getting overrun or a problem with
>a task releasing the scsi bus to another one.
>The fact that the problem only occurs either when 2 drives are heavily loaded
>or when an error condition happens - which appears from the LED activity 
>to tie the bus up for a spell - should be a major clue.  I absolutely
>cannot cause this failure by any combination of loading on one drive.

The problem, in this instance anyway,, is the Newbury drives.  Newbury
SCSI hard drives do not correctly support SCSI bus arbitration.  That
is what causes the hang condition when there is more than one drive in the
system.  I had another customer that had the same problem and Newbury
finally admitted the problem.

			Roy Neese
			Adaptec Central Field Applications Engineer
			UUCP @ {texbell,attctc}!cpe!adaptex!neese

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