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List:       freebsd-scsi
Subject:    Re: 520byte sector size
From:       dan () math ! berkeley ! edu (Dan Strick)
Date:       1998-11-18 23:26:51
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> > I believe the correct method is to change the "data bytes per phys sector"
> > parameter (bytes 12 and 13, big endian) on the "format parameter page"
> > (page code 3) immediately before reformatting.
> 
> That's not completely true.  The SCSI standard isn't very specific in
> this, and a number of comments and notes that are located in the
> description of block descriptors imply that you can use them to alter
> the (logical) block size possibly requiring a future FORMAT UNIT
> command to get into effect.

I stand corrected.  I had not read the fine print in the SCSI standard(s)
for several years and forgot.  I just checked a couple of disk drives
and discovered that these drives treat the "data bytes per phys sector"
in the "format parameter page" to be unchangeable.  For these drives
you have to set the bock size via a mode select block descriptor.

> > I have a program that lets you manually edit individual fields of
> > mode pages symbolically.  The command sequence would go something
> > like this:
> 
> Hmm, something like scsi -e -m <something> (old SCSI system), or
> camcontrol -e -m <something> (CAM system)?

I am not very familiar with the standard FreeBSD facility since I
have never had to use it, but it does seem to provide an equivalent
capability.  Naturally, I unreasonably prefer the facility that
I invented.

> FreeBSD used to have it for years...

If only I had known, I could have saved myself a lot of effort.
Unfortunately, I only started using FreeBSD about three years
ago.  I wrote the first version of my SCSI utility about ten
years ago.  Such a waste ...  Life is so depressing ...

Dan Strick
dan@math.berkeley.edu

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