Re: Linux 2.4/2.5 SCSI considerably slower than FreeBSD

From: Geert Uytterhoeven (geert@linux-m68k.org)
Date: Sun May 19 2002 - 07:38:36 EST

On Fri, 17 May 2002, Matthias Andree wrote:
> Marco Flohrer has posted an inquiry to de.comp.os.unix.linux.hardware
> [German] <slrnae8q66.go4.marco.flohrer@diamond.csn.tu-chemnitz.de> that his
> Seagate 36ES2 was slow with a DawiControl 2976UW (SYM53C875), only
> around 25 MB/s. I have the same observation with a Fujitsu MAH3182MP
> with an Adaptec 2940UW Pro which is not much faster. Either bus has an
> active LVD/SE terminator.
>
> Single-user mode,
> time dd if=/dev/XXX of=/dev/null bs=65536 count=10240
> (671,1 MB) linear read.
>
> Table shows throughput in decimal MB/s (M = 1,000,000)
>
> 2.5 2.4 FBSD max.
> UWSCSI Fuj MAH3182MP 7200/min 32,1 29,4 35,1 TQ 40
> UDMA66 Max 4W060H4 5400/min 27,1 26,7 25,7 66
> UDMA66 IBM DTLA307045 7200/min 37,2 37,5 37,2 TQ 2.5 66
> UDMA66 WDC AC420400D 5400/min 15,5 15,5 15,5 TQ 2.5 66
> --------------
> table is in decimal MB/s.

I used to get 17 MiB/s with a Quantum Viking II U2W connected to the wide chain
of a DawiControl 2976UW (SYM53C875) on my PPC box. This was using the old
sym53c8xx driver (don't remember whether I ever rerun the test with sym2).

I just reran the test (both dd and hdparm) using my current kernel
(2.4.17-pre2, using sym2) and I got only 12 MiB/s.

Gr{oetje,eeting}s,

                                                Geert 

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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