Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!rpi!uupsi!TALOS!jerry
From: jerry@talos.npri.com (Jerry Gitomer)
Newsgroups: comp.arch
Subject: Re: Write-back controllers
Message-ID: <2112@talos.npri.com>
Date: 1 May 91 16:15:51 GMT
References: <3400@crdos1.crd.ge.COM>
Organization: NPRI, Alexandria VA
Lines: 30

davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) writes:


:  After all the discussion of write back and write thru controllers, in
:flavors dumb, smart, and brilliant, I got a chance to do an actual test
:on one the other day, and I thought I'd mention the results. Note that
:these are the results of a single test, under unfavorable conditions. I
:expect to get more formal testing done in the future.

	[configuration details omitted]

:  The system is being used for software development of a LARGE
:proprietary system. The system is configured such that changing certain
:things makes it desirable to recompile everything because of multiple
:dependencies. Using the WD1007 or Ultrastor 22 in normal mode, this took
:26 minutes clock time. When the new driver was installed and the write
:back enabled the time dropped to 15 minutes. CPU time is 13.2 minutes.

:  Whatever the drawbacks of write back, for this application the factor
:of two improvement in performance makes them irrelevant. Installation of
:a UPS, combined with regular backups, put the reliability at an
:acceptable level.

	In a development environment I too would opt for performance, but 
	I hope that my bank uses write-thru.

-- 
Jerry Gitomer at National Political Resources Inc, Alexandria, VA USA
I am apolitical, have no resources, and speak only for myself.
Ma Bell (703)683-9090  (UUCP:  ...uunet!uupsi!npri6!jerry )