[bananas] Linux systems with EIDE: use hdparm!

[Patrick P. Murphy]

Greetings.  This is just a brief note to announce some new AIPSMarks and
to issue a heads-up to those with Linux IDE-based disks.

The results I've just added to the DDT page include an AIPSMark(93) of
27.2 for a 600-MHz Athlon (loaded; half a Gigabyte of RAM, cost about
US$3k), and 18.4 for a lower-end 650-MHz Athlon (bare bones, 128M RAM,
cost under $1k).  Apologies to the submitters of these results; they've
been languishing in my Inbox for way too long; and belated thanks to them
for supplying the details.

The heads-up I wanted to issue is related to the use of "hdparm" to tune
IDE based hard disks on Linux systems.  A generic install of most Linux
distributions will *not* tune your disks, as far as I can tell (at least
not under recent Red Hat releases).  Here at NRAO/CV we have been
routinely adding a line to each system's /etc/rc.d/rc.local that has
something along the lines of:

           /sbin/hdparm -c 1 -d 1 -k 1 -m 16 /dev/hda

This is what I personally have on my desktop system.  Some of these are a
little aggressive (especially the -m 16), but I haven't had any problems
with it to date (knocks on wood).  The effect of using or not using hdparm
can come close to doubling the AIPSMark(93) you may get, and the
performance boost is (qualitatively) very noticeable in non-benchmark use
too.

Rather than bore all of you with a detailed explanation of the various
parameters, I would urge any of you running Linux on IDE or EIDE based
systems to check out the manual page for hdparm.  You can use its "-t"
option for timing tests before and after applying the tuning parameters.

As with any system tuning, caution is required.  Please *read the fine
manual pages* before trying anything, and make sure the settings you
choose are valid for the hardware you possess.  

				- Pat

PS. the DDT page is http://www.cv.nrao.edu/aips/ddt.html and the main AIPS
    pages are at http://www.cv.nrao.edu/aips/
-- 
  Patrick P. Murphy, Ph.D.            Division Head, Charlottesville Computing
  (804) 296-0372, 296-0236                National Radio Astronomy Observatory
  Home: http://www.goof.com/~pmurphy/   Work: http://www.cv.nrao.edu/~pmurphy/
   "Linux is Inevitable."  "Why?"  "Because it's alive!" - John MadDog Hall