Subject: SCSI/disklabel questions
To: None <port-hp300@NetBSD.ORG>
From: Michael Wolfson <>
List: port-hp300
Date: 06/22/1998 20:41:57
Hi folks, I've got a few burning questions.

I recently got my hands on a reasonably fast SCSI-2 drive.  On other
platforms, I can get a sustained transfer rate of well over 3.5 MB/s on
slow/narrow SCSI.  On my 400s, the best I've ever seen is 700 KB/s (actual
elapsed time, not processor time).

Where does the slowdown come from:  the SCSI hardware chipset in the 400,
or the BSD drivers (i.e. will performance get better once people devote
time to writing improved SCSI code)?

Next, on the topic of disklabels, I seem to recall a discussion a while
ago about labeling a drive that doesn't necessarily have perfect geometry
(or unknown geometry).  I don't believe there was any real consensus on the
topic.  Could someone semi-authoritatively comment on the following:

Use default disklabel or (if known) drive parameters (e.g. from  Note, I've never gotten the default disklabel to
    be reasonable, the cylinders are always set to 1.

If not a divisible number of sectors, how to lay out the disk (i.e.
    presume that the last cylinder is only partially filled)?

What's the most efficient setup for ccd (i.e. disk striping)?  I could
    only get ~600 KB/s out of two 2213A drives, but measured ~610 KB/s
    when they weren't arranged in ccd.

Does geometry *really* affect performance on slower workstations/drives 
    (e.g. a HP-IB disk on a 320)?

Is sector 0 in the disklabel the inside of the disk or outside, and
    wouldn't it make sense to put swap on the inside for best performance?

How are the bootblocks and disklabel arranged?  As best as I can
    determine, the label sits at sector 1, and the boot blocks surround it
    at sector 0 and 2 thru whatever.  This would make sense since improperly
    installed boot blocks can be wiped out by disklabel and vice versa.

The install notes recommend ofsetting the a partition by one cylinder,
    which is fine for disks with small cylinder sizes, but how much space
    is really necessary for SCSI disks?

What other NetBSD platforms can/can't write disklabel and bootblocks for 
    hp300 machines (I know sun3x, sun3, and sparc can't)?

On a slightly different track: what SCSI DAT drives are supported, and how
    does one go about getting more models supported?  I have a HP C1504C
    DAT (a.k.a. 35480A) from a 730 that's not recognized (and thus not

And, lastly, can anyone comment on why the HP-IB isn't available when one
    or more SCSI devices are attached (i.e. can't use HP-IB drives or
    tapes if a SCSI drive is plugged into my 400s)?  This used to work
    thru NetBSD-1.1.

  -- MW