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Date:      Sun, 25 Feb 1996 10:49:39 +0100 (MET)
From:      J Wunsch <j@uriah.heep.sax.de>
To:        freebsd-scsi@freebsd.org
Cc:        petzi@zit.th-darmstadt.de (Michael Beckmann)
Subject:   Re: Block size on hard disk
Message-ID:  <199602250949.KAA14773@uriah.heep.sax.de>
In-Reply-To: <v02140b00ad54e4dbfbcc@[130.83.177.1]> from "Michael Beckmann" at Feb 24, 96 05:47:25 pm

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As Michael Beckmann wrote:

> I have a 4 GB SCSI disk (DFHS) from IBM in my system, attached to an NCR
> 810 controller. It is formatted for 512 bytes per block, like mosts hard
> disks. I noticed that the disk can be formatted for 512, 1024 and 2048
> bytes per block.

There are enough disks around which you could format to any weird
sector size.  Something like ``must be between 2 and 65536 bytes'' or
so.

> I was thinking whether it would be wise to reformat it for
> 1024 B/block.

The current ufs implementation doesn't grok it.  I've got patches in
the queue from some Japanese guy to fix this, since it is also needed
for MOD's where you gotta live with them being hard-sectored.  1024
bytes per sector are frequent there, and he told me about rumours that
some newer drives come with media up to 4096 bytes per sector.

(Though i think the latter will result in a huge waste of disk space,
since the ufs fragment size must be at least as big as the physical
sector size.  See the daemon book for wastage figures.)

If you are interested to test the patches, i'm more than happy to
forward it to you.

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)



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