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From: mjr@hussar.dco.dec.com (Marcus J. Ranum)
Newsgroups: comp.unix.ultrix
Subject: Re: Maxtor disks & DEC5000
Keywords: Help
Message-ID: <1990Oct11.211023.2207@decuac.dec.com>
Date: 11 Oct 90 21:10:23 GMT
References: <768@inesc.UUCP>
Sender: news@decuac.dec.com (Network News)
Reply-To: mjr@hussar.dco.dec.com (Marcus J. Ranum)
Organization: Digital Equipment Corp., Ultrix Resource Center
Lines: 34

In article <768@inesc.UUCP> pjd@inesc.UUCP (Paulo Jorge Delgado) writes:
>	We have installed the following configuration:
>
>DECstation 5000/200 (RISC)	- ULTRIX 4.0	- Maxtor XT-8380S
>
>DECstation 2100 (RISC)		- ULTRIX 4.0	- Maxtor LXT-200
>
>	The disks are rated at 14.5ms and 15ms typical seek time against 24ms
>for DEC's RZ55 disks, but I am getting very bad performance ratios for the
>Maxtor disks, using the DISKPERF benchmarks:

	Depending on the way you anticipate using your system, you might
want to increase the size of your buffer cache, and change the write
scheduling policy to delay scheduling dirty buffers for write. This is
done by changing /sys/conf/mips/param.c from:

int	delay_wbuffers = 0;
to
int	delay_wbuffers = 1;

	and running a kernel based on that. Bumping the size of the cache
can be done in the system config file by putting a line like:

	bufcache 20

	which causes the system to use 20% of its memory for cache. This
can make a pretty big difference, **depending on your application**. You're
in the land of trade-offs, and there's no such thing as a free lunch. I
haven't tried tuning the rotational delay of Maxtors - you might want to
play with that some, too.

mjr.
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