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Date:      Fri, 31 Jan 2003 11:22:59 -0600 (CST)
From:      Chris Dillon <cdillon@wolves.k12.mo.us>
To:        joe mcguckin <joe@via.net>
Cc:        hardware@FreeBSD.ORG
Subject:   Re: DLT tape not streaming
Message-ID:  <20030131111850.I4402@duey.wolves.k12.mo.us>
In-Reply-To: <BA5EEC45.1F66F%joe@via.net>
References:  <BA5EEC45.1F66F%joe@via.net>

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On Thu, 30 Jan 2003, joe mcguckin wrote:

> Our DLT-7000 tape drive does not stream continuously - there's quite
> a bit of shuttling back and forth.
>
> Are there any SCSI parameters I can tweak to improve it's
> performance?

Assuming you can actually read the data off the disks and/or network
fast enough, if you can't seem to feed the drive enough data across
the SCSI bus to keep it streaming then you aren't using a large enough
block size.  If you're trying to feed the drive 512-byte blocks, that
is likely not going to work.  I would recommend somewhere between a
32KB and 128KB block size for a DLT drive.  I use 64KB blocks with my
DLT1 drive, but I think that is also the maximum block size in Windows
NT, which is what the drive is attached to.  I think FreeBSD supports
up to 128KB blocks.

--
 Chris Dillon - cdillon(at)wolves.k12.mo.us
 FreeBSD: The fastest and most stable server OS on the planet
 - Available for IA32 (Intel x86) and Alpha architectures
 - IA64, PowerPC, UltraSPARC, ARM, and S/390 under development
 - http://www.freebsd.org

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