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Xref: sserve comp.os.linux:52040 comp.sys.ibm.pc.hardware:63630 comp.os.386bsd.questions:4314 Path: sserve!newshost.anu.edu.au!munnari.oz.au!constellation!osuunx.ucc.okstate.edu!moe.ksu.ksu.edu!vixen.cso.uiuc.edu!uwm.edu!spool.mu.edu!olivea!decwrl!decwrl!doc.ic.ac.uk!pipex!uunet!ogicse!psgrain!percy!leop From: leop@percy.rain.com (Leo) Newsgroups: comp.os.linux,comp.sys.ibm.pc.hardware,comp.os.386bsd.questions Subject: Re: SCSI buyers information Message-ID: <CBGKDI.655@percy.rain.com> Date: 8 Aug 93 20:46:29 GMT Article-I.D.: percy.CBGKDI.655 References: <CAxpDo.L5q@agora.rain.com> <23aknf$jjc@bright.ecs.soton.ac.uk> <PCG.93Aug1215110@decb.aber.ac.uk> <6693@sixhub.UUCP> Organization: /etc/organization Lines: 50 davidsen@sixhub.UUCP (Wm E. Davidsen Jr) writes: >In article <PCG.93Aug1215110@decb.aber.ac.uk> pcg@aber.ac.uk (Piercarlo Grandi) writes: >| Only if miraculously enough you manage to run *both* disks at their >| rated maximum speed *at exactly the same time* for any length of time. >| This is not very realistic. Actually, it is incredibly optimistic. The >| idea that a disk that can deliver 2-4MB from the platter is going to >| deliver it over the bus sustained is peculiar. > my experience is that you are correct in practice as well as >theory. Using a 1542B vs. 1742, on the same machine (EISA/VESA >486-66) showed almost no difference in performance, even when >doing things like memory buffered copy from one disk to another. >When you get more than two disks, assuming heavy load, then you >can get some performance problems, but that's a really heavy >load, and I'm not sure if Linux will generate i/o on more than >two disks (since I don't have source handy). There is a similar discussion taking place in comp.sys.ibm.pc.hardware. The benchmarks in the message below seem to indicate quite a difference. Is it due to the difference between drivers on Linux and 386BSD? From: andrew@werple.apana.org.au (Andrew Herbert) Date: 8 Aug 1993 19:25:45 +1000 Newsgroups: comp.sys.ibm.pc.hardware,comp.unix.pc-clone.32bit,comp.periphs.scsi Subject: adaptec 1542B vs 1742A (was Re: Adaptec vs Ultrastor) bob@obiwan.uucp (Bob Willcox) writes: >(this system) running 386bsd. Reading from the raw disk device >does seem to be faster with this system vs. one of my others that >has a 1542B. This is, of course, comparing apples to oranges but ... True, but I found the same thing when I moved from a 1542B to a 1742A, keeping everything else constant. FYI, I've also included some stats from a barracuda. The following stats are all for a i486/33 EISA system. The results were obtained using iozone with a 16 MB test file and 1024 byte transfers, under netbsd 0.8a, and represent bytes/sec throughput (through a FFS filesystem with 8 KB blocks & 1 KB frags). controller/drive combo write read aha1542b + CDC wren 6 (scsi 1) 210241 519955 aha1742a + CDC wren 6 (scsi 1) 435019 1331525 aha1742a + Seagate Barracuda 1 (scsi 2) 1878047 2088450 Note the barra figures are on a lightly loaded system - in single user mode one gets about 1.9 MB/s and 2.6 MB/s write & read performance respectively. :-) Andrew