Re: SMP 2.1.131: SCSI performance extremely poor vs. IDE

Mr. James W. Laferriere (babydr@baby-dragons.com)
Fri, 11 Dec 1998 15:44:21 -0800 (PST)


Hello Ben,

On 10 Dec 1998, Ben Gertzfield wrote:
> >>>>> "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 don't about a benchmark for file removal, Although I'd
try something like 5 plain text of some differant sizes
(IE: 1mb, 10mb, 50mb, 100mb, 1gb), Then 5 compressed of simular
sizes . Then run the removes like thus :

time rm 'file1mb'
...
Hth

> 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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> "Mmm.. slanty.." -- Homer Simpson
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, JimL
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