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From: knob@wizards.staff.Germany.EU.net (Bernard Steiner)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: SCSI_DELAY in kernel config
Date: 22 Apr 1997 23:03:02 GMT
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In article <3358D092.446B9B3D@freebsd.org>,
"Jordan K. Hubbard" <jkh@FreeBSD.org> writes:
> It's the amount of time the SCSI subsystem will wait for devices to
> "settle" before trying to probe everyone. If you don't have any
> ill-behaved tape drives or other SCSI devices with long setup times, you
> can take it out.
Excuse me, but that's a bit of a euphemism,
> You won't affect performance at all, really, you'll just decrease the
> amount of time it takes you to boot the system. Once you're up, it has
> no further effect.
along with this. I have here
(ahc0:4:0): "WANGTEK 5525ES SCSI REV7 3J" type 1 removable SCSI 1
st0(ahc0:4:0): Sequential-Access density code 0x0, drive empty
and if ever the system crashed while the tape was in use, it would take
just about forever to get the silly thing "rewound" and the drive "on-line".
IMHO the scsi system is ill-advised to wait for tape drives to "settle".
Another problem which appears to be along the same lines (judging from the
effects) is that the same tape drive cannot do an mt fsf 1 that takes more
than a couple of minutes; instead, the SCSI system times out and does nasty
things to the rest of the system (instead of simply waiting for the tape to
report success).
The same tape drive works OK on SunOS4.1.3 (well, OK, it didn't *stream*).
Bernard
(Hey, do Walnut creek accept credit card orders by PGP mail ?)