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Date:      Mon, 22 Jan 2001 22:48:01 -0500
From:      Ian Cartwright <icartwright@mediaone.net>
To:        freebsd-scsi@freebsd.org
Subject:   SCSI Speed Question
Message-ID:  <01012222480104.00373@ian.batcave.com>

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I have a question about the speed of my SCSI devices, especially under 
FreeBSD. I currently have an Adaptec 2940U/w Fast/Wide controller with two 
Compaq Fast/Wide hard disks, and Toshiba SCSI II cdrom and an HP SCSI II DAT 
Drive. My question is, is this the optimum configuration to support the 
highest transfer rate for my hard disks? Does the SCSI bus run at the speed 
of the slowest device on the bus or can I run it in asynchronous mode? If I 
can run in async mode, how do I tell FreeBSD to do it?

I guess that's more than one question... ;-)

In case it helps, here's the info camcontrol gave me:

>camcontrol inquiry 0:0
pass0: <COMPAQ MAB3091SC 0814> Fixed Direct Access SCSI-2 device
pass0: 40.000MB/s transfers (20.000MHz, offset 8, 16bit), Tagged Queueing 
Enabled
>camcontrol inquiry 0:1
pass1: <COMPAQ MAB3091SC 0814> Fixed Direct Access SCSI-2 device
pass1: 40.000MB/s transfers (20.000MHz, offset 8, 16bit), Tagged Queueing 
Enabled
>camcontrol inquiry 0:2
pass2: <TOSHIBA CD-ROM XM-3801TA 3386> Removable CD-ROM SCSI-2 device
pass2: 10.000MB/s transfers (10.000MHz, offset 8)
>camcontrol inquiry 0:6
pass3: <HP C1537A L610> Removable Sequential Access SCSI-2 device
pass3: 10.000MB/s transfers (10.000MHz, offset 15) 

Cheers

Ian Cartwright

BTW: I am not subscribed to the FreeBSD SCSI mailing list so please send 
responses directly to me... Thanks.


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