Date: Mon, 1 Apr 1996 12:56:01 -0500 (EST) From: "Stephen F. Combs" <combssf@salem.ge.com> To: Luigi Rizzo <luigi@labinfo.iet.unipi.it> Cc: davidg@Root.COM, dutchman@spase.nl, freebsd-hackers@freebsd.org Subject: Re: HDD cpu usage (IDE vs. SCSI). Message-ID: <Pine.SUN.3.92.960401125132.27558G-100000@combs.salem.ge.com> In-Reply-To: <199604011545.RAA23295@labinfo.iet.unipi.it>
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Years ago we did a series of tests on PC's with IDE/EIDE/ST506/SCSI/etc.... Out of those tests came the following: If single-user O/S use single/multiple IDE(s) If multi-user O/S (WinNT, Unix, QNX, LynxO/S, etc.....) always, always use MULITPLE SCSI Disks w/SCSI Tape Backup. Wherever possible, on server systems, use multiple SCSI with Multiple SCSI controllers Single disk configurations IDE/SCSI were a wash in all configurations tested. The degradation in a multi-user O/S with multiple SCSI disks was less than 5%. With Multiple IDEs the degradation exceeded 50%. These were performed LOOOONG ago. ---- Stephen F. Combs Internet: CombsSF@Salem.GE.COM GE DS&TC Voice: 540.387.8828 Network Services Home: CombsSF-Home@Salem.GE.COM 1501 Roanoke Blvd FAX: 540.387.7106 Salem, VA 24153 LapTop: CombsSF-Mobile@Salem.GE.COM On Mon, 1 Apr 1996, Luigi Rizzo wrote: > Date: Mon, 1 Apr 1996 17:45:05 +0200 (MET DST) > From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> > To: davidg@Root.COM > Cc: dutchman@spase.nl, freebsd-hackers@freebsd.org > Subject: Re: HDD cpu usage (IDE vs. SCSI). > > > >How come the seagate uses twice as much cpu as the quantum? > > > > Because a Pentium-90 is much faster than a 486-100 for certain things and > > most of the %CPU is for total I/O overhead, not just the overhead in the > > device driver. > > Hmmm... if I get it right this means that under certain circumstances > (1 disk, onboard IDE controller, medium-fast CPU) using SCSI instead > of IDE gives you only a very little saving (which BTW is what I am > convinced of, but this has not been the dominating opinion on this > list). > > Luigi > ==================================================================== > Luigi Rizzo Dip. di Ingegneria dell'Informazione > email: luigi@iet.unipi.it Universita' di Pisa > tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy) > fax: +39-50-568522 http://www.iet.unipi.it/~luigi/ > ==================================================================== >
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