RA60 hard error on 4.2BSD

[pes at mitre-bedford.ARPA]

	I understand that hard disk errors with DEC UDA-50 controllers
and RA60/RA80 drives have been a problem for many VAX UNIX installations.
There was an article posted recently to UNIX-INFO by Ed Merrill and Andy 
Linton which addressed bad block replacement and DEC standard 144 and 166
disk media.  However, it did not provide me with a solution to my immediate
problem.

	I'm running 4.2BSD on a VAX11/780 with RA60 disk drives.
Occasionally while executing tasks which have a lot of disk activity, I
get the following errors at the console:

     uda0: hard error, disk transfer error, unit 0, grp 0x0, hdr 0x26aec
     uda0: hard error, SDI error, unit 0, event 0353, hdr 0x0

The second error repeats about 6 times.

	What do these errors mean?  I'm not an expert on device drivers,
but I've got some local opinions that the driver is to blame.  Has
anyone had similar problems or know of a cause?  Or better yet a fix?
Thanks.

Paul Silvey
pes at mitre-bedford.arpa