Path: utzoo!utgpu!attcan!uunet!tank!ncar!mailrus!tut.cis.ohio-state.edu!bloom-beacon!think!ephraim
From: ephraim@think.COM (Ephraim Vishniac)
Newsgroups: comp.sys.mac
Subject: Re: DiskTimer II results for verious disks wanted.
Message-ID: <30248@think.UUCP>
Date: 3 Nov 88 14:11:01 GMT
References: <1449@ucsfcca.ucsf.edu> <29@eplrx7.UUCP>
Sender: news@think.UUCP
Reply-To: ephraim@vidar.think.com.UUCP (Ephraim Vishniac)
Distribution: comp
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 57

In article <29@eplrx7.UUCP> lad@eplrx7.UUCP (lad) writes:
>From article <1449@ucsfcca.ucsf.edu>, by rampil@cca.ucsf.edu (Ira Rampil):
>> In article <16@eplrx7.UUCP> lad@eplrx7.UUCP (lad) writes:

>>>If you're looking to compare the performance of SCSI disks
>>>Disktimer is NOT the way to do it.  Disktimer is not a benchmark,
>>>it favors disks with a 1:1 interleave and it's results do not
>>>reflect real-world disk performance.  Supermac based their whole
>>>marketing scheme around Disktimer, saying their disks were faster
>>>because Disktimer said so.

>>>        Lawrence A. Deleski             |       E.I. Dupont Co.

>> Could it be that DiskTimer favors 1:1 interleave disks because
>> they ARE faster?  Is this in dispute?

>1:1 disks are faster only if the machine they're working on supports
>1:1.  For example, Apple claims that a 3:1 interleave is optimal for
>a Mac Plus, so a disk formatted to 1:1 is going perform slower.
>Disktimer's problem is that it totally bypassed the driver and made
>calls directly to the low-level SCSI routines, totally ignoring the
>OS.  Any disk with a 1:1 interleave performed better in Disktimer no
>matter what machine it was being run on.  There are several other
>reasons why Disktimer should not be seriously considered when
>evaluating SCSI disk performance, but they are very technical in
>nature.

>Disktimer II:  Just say NO.

Time to stop the garbage, Larry.  DiskTimer *does not* bypass the
driver.  DiskTimer calls the disk's driver through the Device Manager.
That's what the Mac file system does, and that's why DiskTimer's
results have some bearing on the performance that a disk makes
available to the file system.  DiskTimer *agrees* with what Apple
*actually* claimed, which is that a Seagate ST225N on a MacPlus with
Apple's driver is optimally interleaved at 3:1.  If your disk or
driver or Mac is different, then Apple's advice is perfectly
irrelevant.

It's also untrue that making calls "directly to the low-level SCSI
routines" (which are part of the OS) gives you the best transfer rates
with 1:1 interleaving.  This is what the disk drivers do, after all,
and that's not the result they get!

I'm amazed that you continue to spout this nonsense.  Just within the
past month, there were a series of articles here (comp.sys.mac)
discussing how someone mistakenly formatted his disk at 1:1 instead of
2:1 and got dismal performance -- plainly shown by DiskTimer!

Try some tests yourself, Larry.  You'll find your foot's been in your
mouth for a long time.

Ephraim Vishniac					  ephraim@think.com
Thinking Machines Corporation / 245 First Street / Cambridge, MA 02142-1214

     On two occasions I have been asked, "Pray, Mr. Babbage, if you put
     into the machine wrong figures, will the right answers come out?"