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SubjectRe: SMP 2.1.131: SCSI performance extremely poor vs. IDE
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Date
>>>>> "Stephen" == Stephen C Tweedie <sct@redhat.com> writes:

Stephen> This "benchmark" is so full of variables that it is
Stephen> utterly meaningless on its own. You are running on two
Stephen> different systems. Is performance repeatable or not?
Stephen> How much memory is in each system? How fragmented are
Stephen> the existing disks? How much of the data is in the
Stephen> buffer cache when you do the rm?

I agree that it's utterly meaningless on its own, but one of the
complaints I receive most often about Linux is that deleting large
files/large directories takes a *long* time on many systems, which
suggests that there is a small problem hidden somewhere.

If there is a better benchmark that I can test with, please let me
know what it is, so that I can get more meaningful statistics.

I received several responses to my report in private mail (I wish
they'd Cc:ed linux-kernel) -- they confirmed what I'd noticed, that
SCSI behavior in Linux lately has gotten slower and slower.

From: "Daniel Roesen" <droesen@gmx.net>
Subject: AW: SMP 2.1.131: SCSI performance extremely poor vs. IDE
To: "Ben Gertzfield" <che@debian.org>
Date: 09 Dec 1998 08:58:33 -0800

I noticed this with an ICP Vortex RAID Controller (100GB Stripeset) attached
to a 4xXeon SMP, too. 5MB/sec with large blocks with bonnie. Not quite
impressive...

*snip*

Ben> This is, frankly, terrible. Since when is IDE three times
Ben> faster than ultra-wide SCSI?

Stephen> IDE command setup latency is a _lot_ lower than SCSI's,
Stephen> especially with UDMA. If all you are measuring is random
Stephen> read seek rates, then yes, IDE can quite easily be faster
Stephen> than SCSI.

But three times faster? Something's not quite right there. :)

Ben

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