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From: gab10@heatwavecd.amdahl.com (Gary A Browning)
Newsgroups: comp.unix.bsd
Subject: Re: IDE vs SCSI-2 using iozone
Message-ID: <a9nd02fU293D01@JUTS.ccc.amdahl.com>
Date: 3 Nov 92 03:52:47 GMT
References: <1992Nov2.085559.18528@ntuix.ntu.ac.sg>
Sender: netnews@ccc.amdahl.com
Organization: Amdahl Corporation, Sunnyvale CA
Lines: 54
In article <1992Nov2.085559.18528@ntuix.ntu.ac.sg>,
eoahmad@ntuix.ntu.ac.sg (Othman Ahmad) writes:
>
> Here are iozone results run on two different machines using different
> hard-disks. The key difference is the IDE vs SCSI-2 hard-disk.
>
> I only use iozone 1, just to be consistent and make the test more
> realistic.
> Most applications do not need more than 1 Megabyte of sequential
> access..
>
>
>
> 386/25 no cache, Maxtor 7120 200Mbyte Hard-disk runnig 386bsd,patched
> to
> Terry's beta.
>
> Writing the 1 Megabyte file, 'iozone.tmp'...3.333333 seconds
> Reading the file...2.483333 seconds
>
> IOZONE performance measurements:
> 314573 bytes/second for writing the file
> 422245 bytes/second for reading the file
>
> The test completed too quickly to give a good result
> You will get a more precise measure of this machine's
> performance by re-running IOZONE using the command:
>
> Julian's machine, 486/50, Bustek SCSI-2 1.3G hard-disk(?)
>
> IOZONE performance measurements:
> 683854 bytes/second for writing the file
> 499322 bytes/second for reading the file
>
> The test completed too quickly to give a good result
> You will get a more precise measure of this machine's
> performance by re-running IOZONE using the command:
>From your numbers it looks like the SCSI disk has an on-disk cache; note that
the results for reading the file are comparable but the results for writing
have changed by a factor of 2. When writing, the disk can tell the controller
it is done before it actually writes the data onto the disk. When reading,
it has to be more honest; it has to complete the disk access before it can
acknowledge (assuming the file is not still in the cache from the write
operations).
If you use a larger file size, you can minimize the effect of the cache since
it will be unable to hold all of the data and will have top perform disk
activity.
--
Gary Browning | Exhilaration is that feeling you get just after a
| great idea hits you, and just before you realize
| what is wrong with it.