[comp.unix.i386] Disk performance

zeeff@b-tech.ann-arbor.mi.us (Jon Zeeff) (02/03/90)

I'll send you the results from my disk performance survey.  You should also
use a file system defragmenter (or backup and restore) now and then (it makes
a big difference).


-- 
Jon Zeeff    	zeeff@b-tech.ann-arbor.mi.us  or b-tech!zeeff

fiasco@infoserv.com (Mr. Gircys) (08/18/90)

I recently had to remake my .../spool/news file system because it ran out
of inodes. I remade the file system using default values (9 400) for
the mkfs gap and blks/cyl paramaters. Great, so now I have enough inodes
but I notice that rnews seems to take about twice as long to run. A few
simple tests verified that my new file system was 35% slower than those
created during system installation. (As an aside, let me bash Esix tech
support for once again batting zero - I called and asked them very simply,
what values for gap & blks/cyl does your install use when it runs the 
mkfs command so that at the least, I end up with performance as good as that 
provided during install? Their answer was use the mkfs defaults (that is, 
gap & blks/cyl are not specified), hence that's the way I did it.)

Obviously the system install used more appropriate mkfs values than default,
and a 35% hit in performance was unacceptable; so I experimented and
here are the surprising results (normalized to performance of file systems
created during install):

		   install mkfs     default mkfs     empirical mkfs
	file copy       1                1.35             0.7
	file read       1                1.25             0.5

What's surprising is that without to much effort, I found empirical
mkfs gap & blks/cyl values that improved file reads by 50% over the
file systems as made during the install process (are you listening
Esix?). File copy was improved by 30%. In a way I wish this hadn't
work out like this since now I'll have to remake all my file systems 
since the performance improvements are worth it.

Moral of the story: even you might want to set aside a file system
for a little experimentation and see if you're getting the performance
you paid for.

Story particulars: ESIX 5.3.2, SCSI Adaptec 1542 cont, 150 meg disk.
mkfs gap=16 blks/cyl=1024. 

P.S. The ESIX OS is great; never had any problems with it. However, 
their tech support leaves much to be desired.

P.S.S. Please followup if you know mkfs better than the empirical
level; would be nice to know what I really did.

jr@uplherc.upl.com (J.R. Westmoreland) (08/22/90)

Hardware: Micronics 20 MHz 386 with 10MB ram, WD1007-VSE2 with 2 diskette
	drives and 1 CDC 94186-766, etc.
Software: SCO UNIX system v/386 3.2.0,
	PCDOS v3.3.
Hard Disk Layout: First partition 33MB DOS area.
	Second partition UNIX area.
Problem: The disk performance is very slow under UNIX.  The performance under
	DOS is fast, at least appears to be very fast.  The UNIX area is
	logically devided in to two areas the root and a separate /u area.

Any recommended solutions or suggestions?

Thanks for any help any one might be able to offer.

J.R. Westmoreland