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Date: Tue, 17 Dec 1996 13:14:30 +0100
From: se@FreeBSD.ORG (Stefan Esser)
To: mishania@demos.su
Cc: freebsd-quiestions@FreeBSD.ORG, freebsd-hardware@FreeBSD.ORG
Subject: Re: Seagate Barracuda 9 (11/9) gb specs?
References: <199612170944.MAA03416@megillah.demos.su>
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In-Reply-To: <199612170944.MAA03416@megillah.demos.su>; from Mikhail A. Sokolov on Dec 17, 1996 12:44:52 +0300
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On Dec 17, mishania@demos.su (Mikhail A. Sokolov) wrote:
> Hello, 
> 
> I wonder if someone can help me with the following. I have Seagate UW SCSI
> Barracuda 9 9gb (11 unformatted) drive to rape. Since it's pretty new one, 
> I've been checking it with 2.1.5/2.1.6/2.2-alpha/3.0-current, it works.
> (Ehm, now installing 2.1.0r, just to test ;-))
> The only problem is that when using default geometry, I lack some 
> 400/500mb, i.e. only 8600+mb seen, see dmesg data at the end.
 
Hmmm, 8683*1024*1024 = 9.105 * 10^9 ...

Seagate gives the drive capacity in Million bytes, as just 
about everybody in the disk drive business does, but FreeBSD 
prints the capacity in MByte (2^20) units.

> The question finally is: can any of you name the geometry of it and 
> is it ok that this disk is seen it's 9gb unformatted, and 8,6+ formatted?

The drive really has some 11GB unformatted capacity, and 9GB
formatted, using decimal units. It is typical to loose some 
20% for intersector gaps, which may contain servo information,
but are required to allow for variations in rotational speed,
and for activating and deactivating the write head, too.

It is common to use decimal MB for capacities, but for (some)
data rates, too. For example, a 10MB/s FAST SCSI bus is limited
to 9.5*1024*1024 bytes, since it actually operates at 10MHz.
(The same is true of EIDE speed specifications, BTW :)

> ahc0 <Adaptec 2940 Ultra SCSI host adapter> rev 0 int a irq 10 on pci0:12
> ahc0: aic7880 Wide Channel, SCSI Id=7, 16 SCBs
> ahc0 waiting for scsi devices to settle
> (ahc0:0:0): "SEAGATE ST19171W 0018" type 0 fixed SCSI 2
> sd0(ahc0:0:0): Direct-Access 8683MB (17783112 512 byte sectors)

Nice drive! Would love to have one :)

Regards, STefan