BSD Unix machines hanging

[Robert Ruge]

In article <6700001 at ntvax> jeff at ntvax.UUCP writes:
>
>We are experiencing the same symptoms about once every two weeks (average).
>When the gremlin decides to assert him(her)self the terminals die one by
>one when they go to disk.  Anybody running an application that doesn't
>require a disk access can run forever even though every other terminal
>has died (including the console).  Once they exit from that application,
>they're history.  We're running 4.2 on a 780 with Massbus rm80s and an rp07.
>Any ideas?
>

I recently experienced this problem on a Gould PN6031 and traced it
down to a bad block on one of the disks. Whenever this block was
accessed the disk controller would hang so that when a program or user
went to access the disk they would also hang waiting for the disk
controller to complete its operation. However if your program is
running in memory then you can execute for as long as you like, until
you either finish execution or perform a disk access. This results in
terminals going out one by one. To find the bad block we wrote a small
program that opened the c partition (whole disk) and sequentially read
each sector and printed its number. Where the program stopped is where
the bad block is. Flagging the block as bad cleared up the whole
problem. I hope that this helps you.

Robert Ruge	  | UUCP:   {seismo,mcvax,ukc,
Computing/Maths	  |          hplabs,nttlab}!munnari!aragorn.oz!robert
Deakin University | ARPA:   munnari!aragorn.oz!robert at SEISMO.ARPA
Victoria, 3217	  | CSNET:  robert at aragorn.oz
Australia	  | ACSNET: robert at aragorn.oz  PHONE:  +61 52 471319