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Path: utzoo!mnetor!seismo!rutgers!princeton!allegra!ulysses!mhuxt!ihnp4!alberta!auvax!rwa
From: rwa@auvax.UUCP
Newsgroups: comp.sys.misc,comp.periphs,comp.unix.wizards
Subject: Re: magtape, and what's hot
Message-ID: <161@auvax.UUCP>
Date: Wed, 6-May-87 16:25:05 EDT
Article-I.D.: auvax.161
Posted: Wed May  6 16:25:05 1987
Date-Received: Sun, 10-May-87 09:12:19 EDT
References: <878@wjvax.wjvax.UUCP> <242@uwslh.UUCP> <6567@mimsy.UUCP>
Distribution: na
Organization: Athabasca U., Alberta, Canada
Lines: 39
Summary: you can get 'em to go faster'n _that_ !
Xref: mnetor comp.sys.misc:566 comp.periphs:369 comp.unix.wizards:2241

In article <6567@mimsy.UUCP>, chris@mimsy.UUCP (Chris Torek) writes:
> But you may not be able to use all that speed.  DEC disk drives
> tend to have low peak practical (by which I mean `file system style'
> through the raw device, i.e., /etc/dump) transfer rates:  I have
> never observed more than 130KB/s from RA81s; I think our RP06s top
> out below 200KB/s.  Our Eagles, on an Emulex SC78x, occasionally
> send more than 600KB/s, but more usually run in the 200 to 500 KB/s
> range.  (Try running systat or iostat while dumping a drive to
> /dev/null.)

Ok, I just did that.  "dump 0f /dev/null /dev/rra1h & iostat 1".
System is an 11/785, 24 megs of core (whoops, RAM) running Ultrix
1.2; interface to the ra81 is via uda50 sitting on a private
unibuss/dw780 (actually shared with a deuna, but net traffic is
light), said uda50 has the 'buss-wait' jumper set to zero.
Measurements were made under light load (load avg.  about 2, 33
users, at about 2 in the afternoon).  Iostat reported average
transfer rates in the 290 Kb/s to 350 Kb/s range.  /dev/ra1h is an
8k/1k filesystem of about 360 megabytes.  The main hack here was to
set the burst-transfer counts higher.  Look at the comments in
/usr/sys/data/uda_data.c about hog-mode and try setting ud_burst to
something larger than the default 0 (I am using 3, but maybe even
higher would work ?  I _must_ sit down and experiment!  OK, everybody
off the machine _NOW_!!  ).  At-any-rate, ra81's aren't complete
slugs.  But Chris is right, the machine _still_ can't keep up to the
tape drive when dumping.  The pauses for thought are obvious.

As an aside, until I put the uda50 and deuna onto their own unibuss,
auvax was a very unstable machine.  All kinds of terminal wedging, net
crashes, and general unpleasantness.  Blecherous.  And the disks
were slow then too.

Private to Chris:  how did you get your eagles to go so fast?  I
have some tied to a 780 via an SI 9900 and I don't think I ever saw
+500 (or even +300) Kb/s out of them.  Suggestions gratefully
accepted :-).

--
...!ihnp4!alberta!auvax!rwa	Ross Alexander, Athabasca University