From: "Kevin Hui - DCS" <khui@cs.toronto.edu> To: "Alfred Perlstein" <bright@mu.org> Cc: <freebsd-questions@freebsd.org> Subject: Re: Experiencing very slow raw write speeds on /dev/ad1 Message-ID: <007001c12158$b2ee87e0$07010101@mtwx1.on.home.com> References: <Pine.GSO.4.21.0108091853190.5157-100000@gardiner.cs> <20010809190350.M85642@elvis.mu.org>
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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 > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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