INTEL 5.4 2.0 and Adaptec 1542B

[Seckin Unlu]

In article <1991May20.145226.7155 at march.co.uk>, rossw at march.co.uk (Ross
Wakelin) writes:

> The INTEL 5.4 release 2.0 (developers edition) has buggy drivers for the
> Adaptec 1542B SCSI host adaptor.
> 
> We were using this adaptor in a 25Mhz Mylex 486 motherboard, and achieved 
> a record number of system lockups and crashes.  The machine would go away
> for a minute or so and then report a SCSI error.  At this point, our only 
> option was to reboot the machine.

The problem was:  On a Read-Extended (0x28) command, the disk would
send a disconnect message to the adapter, the SCSI bus would become
free, the disk would not reconnect, the driver would time out after
30-90 seconds, retry the read-extended, but the SCSI bus would hang.

The problem was seen mostly with AHA-1540 and Maxtor XT-4000S series,
occasionally with WD-7000 FASST2 and XT-4000S, and never with other
combinations of adapters and disks.

> We replaced the 1542B with a WD-7000 FAST card, and found that we still got
> the SCSI errors, but the driver for the WD board recovered from the errors
> and let us continue processing.  Needless to say, we are now production on
> the WD board.

The WD-7000 FASST2 driver in SVR4 resets the adapter and the SCSI bus 
before retrying commands.  The Adaptec driver in SVR4 2.0 didn't.
In SVR4 3.0, the Adaptec driver sends a Bus-Device-Reset message
to the locked-up disk, before retrying the command.  This workaround
seems to work most of the time.

> Hopefully this is one of the things that was (will be) fixed in the
> handover to Interactive.

> Ross Wakelin                                        r.wakelin at march.co.uk
> Unix Systems Director                   or ..mcsun!ukc!slxsys!march!rossw 
> March Systems Consultancy Ltd 

These are the workarounds to the above problem:

- If the disk is a Maxtor XT-4000S, make sure f/w is at B5D level,
  and disable the read-ahead cache on the disk.  No more lock-ups,
  but sequential read performance will be lower.

- Use another disk (even with Maxtor XT-8000S the problem goes away).

- Use another adapter (e.g. WD-7000 FASST2, what you have done). The
  problem does not go away, but it is less frequent and less fatal.

- Get SVR4 3.0, from Interactive Systems Corporation.

I hope this helps.

Seckin Unlu            uunet!littlei!seckin  or  seckin at littlei.intel.com
Software Engineer                            or  seckin at sumac.intel.com
Intel Corporation
-----
Any opinions expressed here are my own and
are not representative of Intel Corporation.