Date: Sat, 6 Sep 1997 23:40:24 +0200 (MEST) From: Søren Schmidt <sos@sos.freebsd.dk> To: mal@algonet.se (Mats Lofkvist) Cc: current@FreeBSD.ORG Subject: Re: lousy disk perf. under cpu load (was IDE vs SCSI) Message-ID: <199709062140.XAA07333@sos.freebsd.dk> In-Reply-To: <199709061909.VAA25891@kairos> from Mats Lofkvist at "Sep 6, 97 09:09:41 pm"
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In reply to Mats Lofkvist who wrote:
> For fun I tested the dd benchmark on my new machine (intel providence
> board with pp200, 64M, quantum viking 4.5G uw connected to the aic7880).
>
> As long as I run the dd with the machine idle, I get over 10MB/s.
> But with a single cpu-bound process running, the throughput drops
> to less than 1.5MB/s with 64k blocks (and it gets even worse with
> smaller blocks).
Hmm juist tried this on current with EIDE disk and DMA turned on:
Machine is a P6@233/64M/Maxtor EIDE/current as of just now...
Nice -19 loop (being a tight CPU loop).
# dd if=/dev/rwd0 of=/dev/null count=800 bs=64k
800+0 records in
800+0 records out
52428800 bytes transferred in 10.904597 secs (4807954 bytes/sec)
This is about half the rate as on an unloaded system...
So maybe this is handled better in current, or EIDE w/DMA is not
as bad as people think. The only advantage with SCSI these days
seems to be the ability to add more than 4 devices easily, and
to add them externally of the machine. But then again you have to
pay solid bucks to get that :)
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Søren Schmidt (sos@FreeBSD.org) FreeBSD Core Team
Even more code to hack -- will it ever end
..
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