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From: kinsell@hpfcdj.HP.COM (Dave Kinsell)
Newsgroups: comp.sys.hp
Subject: Re: Help - I have two identical disks - and one is very slow.
Message-ID: <17330030@hpfcdj.HP.COM>
Date: 2 Mar 91 21:49:29 GMT
References: <BB.91Feb26004149@reef.cis.ufl.edu>
Organization: Hewlett Packard -- Fort Collins, CO
Lines: 45


>I suspect that a disk's performance may be hurt this badly by an
>inappropriate filesystem layout and/or tunable perameters.  What I
>would like to see would be:
>
>	1.  Confirmation that my suspicions are reasonable.

	They're reasonable, but the tuning has a bigger
	impact on sequential throughput than on random activity.
	The execution of 'ls' would generate little sequential
	activity, with the exception of the load of 'ls' itself,
	if needed.

	My first guess would be an uneven workload on the disks,
	or some strangeness caused by the networking configuration.

>	2.  Confirmation of an appropriate /etc/disktab entry.

	They match what we sent out.

>	3.  Suggestion of some way to read the mkfs parameters
>	    back off of both disks for diagnostic purposes.
>
	The tuning info is much easier to come by than the block
 	sizes.  Tunefs gives you the old and the new values.  Look
	for 4 ms rotdelay and maxcontig of 1 for the best performance
	with those disks.  If they're not right, rebuilding the file
	systems would be necessary to give you full advantage of the
	proper tuning.

	Another thing to look at is the possibility of a marginal
	disk that might be having trouble reading data.  Look in
	msgbuf via the dmesg command to see if a large number of
	I/O errors are being reported for the drive.


>Thanks.

>Brian Bartholomew	UUCP:       ...gatech!uflorida!beach.cis.ufl.edu!bb
>University of Florida	Internet:   bb@math.ufl.edu


David Kinsell

paid by, but not representing, Hewlett-Packard