disk sequencer error

[msommer at watson.bbn.com]

> > xy0a: read retry (disk sequencer error) -- blk #495, abs blk #495
> 
> We have received these errors on several different systems (several
> different controller/disk combinations.) Sometimes the disk stops working
> and sometimes we get a couple of the error messages and then things
> proceed normally. 
>...

Dinah,

We were besieged with a bunch of these errors a few months ago on our
3/160, with a 2351A Eagle disk, and a Xylogics 450 controller. 

Our problem was caused by a low voltage near the controller board's
backplane slot. Luckily, our Sun field service rep had heard reports of
such a problem (though he had never seen it before, himself), and knew
exactly what to check. Once he found the problem, he just tweaked the
voltage and, presto, the errors disappeared.

If this is the cause of your (and others') problems, and you've called Sun
about them without any success, it suggests there's a lack of
communication among Sun f.s. reps.  

I should note our 3/160 was originally a 1/160 or 2/160. The CPU board and
power supply are both Sun 3 models. We upgraded our power supply after
suffering repeated crashes (several months after the CPU board was
upgraded, when we tried to add a memory board). The backplane, however,
has never been upgraded. My intuition tells me this may have something to
do with the voltage problems. People should probably avoid upgrading their
systems in such a piecemeal fashion. 

mark sommer
msommer at bbn.com