Date: Tue, 16 May 2000 11:20:57 +0930 From: Greg Lehey <grog@lemis.com> To: Ian Cartwright <ICartwright@IT.RJF.com> Cc: freebsd-scsi@freebsd.org Subject: Re: SCSI Speeds? Message-ID: <20000516112057.A10269@freebie.lemis.com> In-Reply-To: <6D5097D4B56AD31190D50008C7B1579B91204C@EXLAN5> References: <6D5097D4B56AD31190D50008C7B1579B91204C@EXLAN5>
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On Monday, 15 May 2000 at 10:23:14 -0400, Ian Cartwright wrote: > Hello, all. > > I have a question regarding the relative speeds of devices on a SCSI bus. I > have two machines currently running FreeBSD. One is a P-200 with IDE and one > is a PII-360 with both IDE and SCSI drives. I boot off the the SCSI bus on > this machine. The IDE drives on both machines are UDMA-33. My SCSI drives > are as follows (reported by FreeBSD on boot up): ID0: Fast SCSI2 HDD 10.00 > MB Xfer (Synchronous), ID1: Ultra SCSI2 HDD 40.00 MB Xfer (Synchronous), > ID2: SCSI2 CD-ROM 10.00 MB Xfer (Async), ID4: SCSI CD-Writer 3.300 MB Xfer > (Async), ID5: SCSI2 Tape (Xfer not reported, Asynch). > > My question is this: why does it seem that the slower machine does disk > access much faster? When I was installing these machines newfs wrote > superblocks to the IDE drives much faster than to the SCSI drives, even > though the Ultra SCSI drive (my FreeBSD drive) should theoretically be much > faster... Many disk intensive operations seem to be faster on the IDE > drives. Any ideas as to why this should be? The IDE disks are probably just simply faster. Don't confuse the transfer rate with the disk speed. No drives I know of can currently hit 33 MB/s, so that's not the issue, and some recent IDE drives are blindingly fast. If you want to check, run rawio (/usr/ports/benchmarks/rawio) against the drives and see what speeds it comes up with. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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