From owner-freebsd-hardware  Fri Mar 12  9:28:57 1999
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From: Edwin Mons <e@ik.nu>
Message-Id: <199903121728.SAA13022@mag.ik.nu>
Subject: Re: SCSI ZIP slow transfers
In-Reply-To: <199903121718.KAA32574@panzer.plutotech.com> from "Kenneth D. Merry" at "Mar 12, 99 10:18:51 am"
To: ken@plutotech.com (Kenneth D. Merry)
Date: Fri, 12 Mar 1999 18:28:22 +0100 (CET)
Cc: hardware@freebsd.org
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> Edwin Mons wrote...
> > Hi.
> > 
> > I use FreeBSD 3.1-RELEASE at home, and have a SCSI ZIP drive attached
> > to an NCR-810 controller.  When reading or writing DOS disks, I can read
> > and write at 97 KB/s max.  If the disk is a UFS ZIP, transfer speeds of 
> > 400 KB/s can be reached, but if I dd the raw data from either one of these
> > two disks, speed is reduced to 97 KB/s again.  After enabling CDB debugging 
> > for the ZIP drive I noticed that when accessing the UFS ZIP data is read
> > in 64 KB blocks, while when reading raw data (with dd) or a DOS disk, the
> > blocksize is 4KB.
> > 
> > Can anybody explain this to me?  I more or less expected to see the 4 KB
> > blocksize when accessing the DOS partition (8 sector cluster layout), but
> > I can't explain the 4 KB blocks for raw reads.
> 
> What arguments did you use with dd?  Did you specify 64k blocks when
> reading from the raw device?

I used `dd if=/dev/rda0 of=/dev/null bs=64k` to read the disk.  I'm not at my
own system at the moment, so I can't give more details (/var/log/messages,
exact rates, etc.).

Regards,
Edwin Mons


 Edwin Mons                      | ...and the LART shall reign, and the 
 e@ik.nu                         | daemons shall conquer the evil fortresses
 http://www.mons.net             | of the beast of NT and their leagues of
 FreeBSD - the power to serve    | management and MicroDrones...


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