Date: Fri, 12 Mar 1999 17:51:08 -0600 From: Chris Csanady <cc@137.org> To: Darryl Okahata <darrylo@sr.hp.com> Cc: freebsd-scsi@FreeBSD.ORG, ken@plutotech.com Subject: Re: SCSI disk oddities and Buslogic problems.. Message-ID: <19990312235108.302BFAB@friley-185-205.res.iastate.edu> In-Reply-To: Your message of "Fri, 12 Mar 1999 15:12:25 PST." <199903122312.PAA12555@mina.sr.hp.com>
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Well, therein lies the problem. When I disable disconnection on these drives,
the performance is just as advertised. So, does it mean that the problem
is likely driver related?
Chris
>sthaug@nethelp.no wrote:
>
>> Chris Csanady <cc@137.org> wrote:
>> > In this case, I have found that while running the following commands that
>> > the data transfer is very erratic.
>> >
>> > dd if=/dev/rda2s3 of=/dev/null bs=128k (or any place on the disk..)
>> >
>> > iostat -w 1 da2
>>
>> No problem with a 9 GB model here. Typical iostat output:
>
> I have seen strange things with 3.1-RELEASE (I've yet to try
>-current), and tagged queueing. Using 3.1-RELEASE, an Adaptec 7895
>controller (built into my Gigabyte 6BXDS motherboard) and two IBM
>Ultrastar 9ES drives striped together using vinum, I get strange
>performance numbers using iozone (yeah, iozone isn't very good for
>benchmarking striped drives, but I'm just using it as a zero-th order
>gauge).
>
> Individually (if I do not use vinum and just newfs a single drive),
>I get around 11MB/s write, and 13MB/s read. No problem here.
>
> If I stripe the drives together using vinum, and use the default
>newfs values, I get something like 3.7MB/s write, and 16MB/s read. The
>write throughput sucks. If I run newfs with 4K frag sizes, the write
>throughput jumps up to around 7MB/sec. Better, but still not great.
>
> However, if I go into the BIOS and disable SCSI disconnect, the
>write throughput jumps back up to 11MB/s. Much better, but disabling
>disconnects kinda defeats the purpose of striping ....
>
> The only thing I can think of is that tags are somehow involved, as
>disabling disconnects also disables tags.
>
> However, one slightly unusual thing about the striped drives is
>that one drive is a plain fast/wide disk ("IBM DDRS-39130W S97B"), and
>the other is the LVD version running in single-ended mode ("IBM
>DDRS-39130D DC1B"), but this shouldn't matter.
>
>--
> Darryl Okahata
> darrylo@sr.hp.com
>
>DISCLAIMER: this message is the author's personal opinion and does not
>constitute the support, opinion, or policy of Hewlett-Packard, or of the
>little green men that have been following him all day.
>
>
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