From owner-freebsd-hackers Tue Apr 9 11:45:09 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id LAA02539 for hackers-outgoing; Tue, 9 Apr 1996 11:45:09 -0700 (PDT) Received: from Sisyphos (Sisyphos.MI.Uni-Koeln.DE [134.95.212.10]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id LAA02533 for ; Tue, 9 Apr 1996 11:45:06 -0700 (PDT) Received: by Sisyphos id AA05369 (5.67b/IDA-1.5 for freebsd-hackers@FreeBSD.ORG); Tue, 9 Apr 1996 20:44:20 +0200 Message-Id: <199604091844.AA05369@Sisyphos> From: se@zpr.uni-koeln.de (Stefan Esser) Date: Tue, 9 Apr 1996 20:44:20 +0200 In-Reply-To: Kees Jan Koster "HDD cpu usage (IDE vs. SCSI)." (Apr 1, 11:03) X-Mailer: Mail User's Shell (7.2.6 alpha(2) 7/9/95) To: Kees Jan Koster Subject: Re: HDD cpu usage (IDE vs. SCSI). Cc: freebsd-hackers@freebsd.org (FreeBSD hackers Mailing list) Sender: owner-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk On Apr 1, 11:03, Kees Jan Koster wrote: } Subject: HDD cpu usage (IDE vs. SCSI). } Hoi Hackers, } } I was told that cpu usage of SCSI disks was lower than that of IDE disks. Yes, in most situations it definitely is, especially given the lack of EIDE DMA support in FreeBSD (not that I'd need it :) } However: [ indentation and unimportant lines removed ... ] LikeEver (amd486DX4-100, ncr pci scsi controller) -------Sequential Output-------- ---Sequential Input-- --Random-- -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks--- Directory MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU Seagate 20 1299 81.1 1263 15.5 653 18.2 1778 94.9 1982 41.8 47.7 5.7 Maxtor 20 750 41.9 740 8.5 405 9.7 764 34.7 770 8.8 32.0 3.9 phobos (pentium 90, on-board IDE controller) Directory MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU Quantum 40 1215 41.7 1818 18.8 811 11.5 1376 41.0 1990 16.0 39.9 3.9 } How come the seagate uses twice as much cpu as the quantum? How comes the 486 needs twice as much time as a P90 to complete just about any task ? ;-) Honestly: I'm not sure what you are doing in these tests, since the numbers are low for the NCR SCSI as well as the IDE case. I'd guess that both the Seagate and the Maxtor are old drives (or they'd read more than 2MB/s in the "Block Input" test). How about a different test: # time dd if=/dev/rsd0c of=/dev/null bs=64k count=1000 1000+0 records in 1000+0 records out 65536000 bytes transferred in 9 secs (7281777 bytes/sec) 9.32 real 0.02 user 0.24 sys (ASUS SP3G with NCR and Quantum Atlas 2GB.) What are your numbers for both the NCR and the EIDE system ? These numbers indicate less than 3% CPU is required to read 7MB/s (though there are cycles that aren't accounted to the "dd" process and which aren't easily measured). I'd guess that less than 1% CPU is spent on doing the actual transfer on you amd486 system. The remaining CPU time is consumed by file system overhead. Regards, STefan -- Stefan Esser, Zentrum fuer Paralleles Rechnen Tel: +49 221 4706021 Universitaet zu Koeln, Weyertal 80, 50931 Koeln FAX: +49 221 4705160 ============================================================================== http://www.zpr.uni-koeln.de/~se