Path: utzoo!mnetor!uunet!husc6!cmcl2!phri!roy
From: roy@phri.UUCP (Roy Smith)
Newsgroups: comp.periphs
Subject: Re: disk recomendation for sun-3/50
Message-ID: <3091@phri.UUCP>
Date: 27 Dec 87 16:04:05 GMT
References: <2604@aramis.rutgers.edu>
Reply-To: roy@phri.UUCP (Roy Smith)
Organization: Public Health Research Inst. (NY, NY)
Lines: 39

In <2604@aramis.rutgers.edu> marantz@aramis.rutgers.edu (Roy Marantz) writes:
> [...] SCSI disk that I can attach to a SUN-3/50.  I want to use the
> disk for swapping (and maybe /tmp).  I'm hoping this will speed up
> (over nd swapping)

	At the time we were looking at Suns (about 2 years ago; the 3/50's
had just been announced), we were thinking that lots of small disks on the
clients would be faster than sharing a big disk on a server for exactly the
reasons stating in Roy Marantz's article.  We were slavishly following the
Unix truism that "performance is directly proportional to the number of
independant disk arms".

	After some discussions with the folks at sun, we were convinced
that we had the wrong idea.  Sun claims (and I have no reason to doubt
them) that you get better disk throughput with a remote Eagle than with a
local SCSI disk.  In other words, the performance hit you take for going
through the network is less than the difference in speeds between the two
types of drives.

	I recently saw somebody (on Sun-Spots, I think) talking about his
2-disk server; he wanted to put ND partitions on both disks and have each
client mount two swap partions; one on each disk.  I suspect that idea will
win a lot more than buying a SCSI disk to swap on.  I'm very tempted to try
it myself.

	This was two years ago.  I havn't really been paying much attention
to SCSI disks in that interval, so it is possible that they have gotten
fast enough to make the comparison above no longer true.  On the other
hand, SMD disks have gotten faster also (a Super Eagle on one of the new
fast VME controllers should be significantly faster than a plain Eagle on a
XY-450).  One thing I know has changed.  At the time, the cost per Mbyte
curve for disks made the bigger disks a lot more attractive compared to the
20-40-70 Mbyte SCSI disks.  I think small disks have dropped in price
faster than big ones over the past couple years, making the cost per Mbyte
much more even accross the spectrum of disk capacities.
-- 
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016