From owner-freebsd-questions  Thu Aug  9 21:54:21 2001
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From: "Kevin Hui - DCS" <khui@cs.toronto.edu>
To: "Alfred Perlstein" <bright@mu.org>
Cc: <freebsd-questions@freebsd.org>
References: <Pine.GSO.4.21.0108091853190.5157-100000@gardiner.cs> <20010809190350.M85642@elvis.mu.org>
Subject: Re: Experiencing very slow raw write speeds on /dev/ad1
Date:	Fri, 10 Aug 2001 00:55:36 -0400
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Thank you, Alfred, for the hint.

Adding write caching helped a lot.  Now the write speed jumps to ~15.8MB/s
instead of the previous 3.5MB/s.
Are there any other such settings I should pay attention to?  I asked
because I believe that the performance is still not as good as can be.  I
have the rawio program running under Linux with the identical hardware
(accessing the /dev/raw/raw0, which maps to /dev/hdb) and I got ~38.4MB/s
raw write speed (BTW I get ~38.4MB/s from both Linux and FreeBSD when I do
the single-process raw sequential read test).

Thanks,
-Kevin.

----- Original Message -----
From: "Alfred Perlstein" <bright@mu.org>
To: "Kevin Hui" <khui@cs.toronto.edu>
Cc: <freebsd-questions@freebsd.org>
Sent: Thursday, August 09, 2001 8:03 PM
Subject: Re: Experiencing very slow raw write speeds on /dev/ad1


> * Kevin Hui <khui@cs.toronto.edu> [010809 18:10] wrote:
> > Hi all,
> >
> > I have installed 2 Maxtor UDMA100 drives in my system, sharing the
channel
> > ide0.  /dev/ad0 contains all the FreeBSD partitions and ad1 is used as a
> > scratch drive (there's nothing on it). Ide1 channel is used for the DVD
> > drive (which doesn't support UDMA):
>
> FreeBSD 4.3 was released with IDE write caching turned off.  This
> was to help people preserve thier data, but since most IDE disks
> perform so badly with it off it's back on in recent FreeBSD versions.
>
> You can also turn it on by adding the line:
> hw.ata.wc=1
> to your /boot/loader.conf
>
> and please don't cc multiple lists when asking a question.
>
> -Alfred
>


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