spontaneous bad blocks on RL02 disk cartridge

[Brad Hemminger]

  We are having annoying problems with our RL02 disk cartridge drive.
Cartridges in the drive tend to develop hard read errors after being
in use for several days, and end up bringing the system down.  System
is a Vax 11/730 running 4.3BSD.

When testing this I have have done the following...
	1) take RL02 disk cartidge to a sister Vax 11/730
	2) format (2 tracks (0-1) and 32 cylinders (0-31)
	3) make a new filesystem on the cartidge 
		newfs /dev/rb0a rb02
	4) fsck filesystem (no errors)
	5) restore filesystem from 0 level dump tape
	6) fsck filesystem (no errors)
	7) take RL02 cartridge back to original machine
	8) Boot Vax 11/730 (no errors)
	9) run fsck several times a day (no errors)
	10) After 3-4 days generally, the system grinds to a stop
	    because of hard errors on the RL02 cartridge.  (RL02
	    contains /).
	11) Take cartridge back to sister machine
	12) Fsck shows same errors as those seen on original machine
	    in (10)
I have repeated this loop > 10 times with 5 different cartridges (all
cartridges worked fine before).  Hard errors almost always have the same 
sector number (12896), but NOT always.  I don't know whether that is
significant.


I'm looking for good advice on what's going on, and how to solve it; or
as an alternative, I would like to know what other drives one can
get to use instead of the RL02.  The only reason I have the RL02 is because 
I need it to boot the Vax 11/730 (as best as I can tell I cannot boot
my Eagle 4351 directly).  Any inexpensive drives that hold 7 Meg or more
and can boot the 11/730 are acceptable.

Thanks, 
   Brad Hemminger
   Dept of Radiology