Date: Tue, 9 Sep 1997 02:06:08 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: mal@algonet.se (Mats Lofkvist) Cc: current@FreeBSD.ORG Subject: Re: lousy disk perf. under cpu load (was IDE vs SCSI) Message-ID: <199709090206.TAA00939@usr07.primenet.com> In-Reply-To: <199709082256.AAA04008@kairos> from "Mats Lofkvist" at Sep 9, 97 00:56:05 am
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> > There is one issue I would like to return to, and that is the question > > originally posed: lousy disk performance under *some* circumstances. > > (Which circumstances?) > > This is also what I really was interested in, I have heard enough > about the pros and cons of scsi and eide :-) > > Few seem to be able to repeat my data, so here is some more information. [ ... ] > FreeBSD 2.2.2-RELEASE #0: Tue Aug 12 03:02:44 CEST 1997 [ ... ] > ahc0 <Adaptec aic7880 Ultra SCSI host adapter> rev 0 int a irq 10 on pci0:9 > ahc0: aic7880 Wide Channel, SCSI Id=7, 16 SCBs > (ahc0:0:0): "QUANTUM VIKING 4.5 WSE 8808" type 0 fixed SCSI 2 > sd0(ahc0:0:0): Direct-Access 4345MB (8899737 512 byte sectors) > ncr0 <ncr 53c810a scsi> rev 18 int a irq 10 on pci0:17 > (ncr0:0:0): "QUANTUM VP32210 81H8" type 0 fixed SCSI 2 > sd1(ncr0:0:0): Direct-Access > sd1(ncr0:0:0): 10.0 MB/s (100 ns, offset 8) > 2103MB (4308352 512 byte sectors) It is unclear to me whether you are having problems on the disk on the NCR controller or the Adaptec controller. The fact that you are running 2.2.2 does not fill me with hope; I was under the impression that 2.2.2 did not support tagged command queueing on the NCR, at least, and perhaps not the Adaptec as well. This would mean that you could have only a single concurrent operation outstandaing at one time -- which would certaily explain the performance problems you are seeing. You will have to check the list archives, but I believe there were also a number of issues with the 53c810a. I have several 53c810b's, so I can't test for you. My only Adaptec at this point in time is the 1742B in my EISA machine; it's not a fair comparison, since the bus is overclocked. I have gotten fabulous perforamnce figures on my NCR 53c810b under 3.0, but I've been using a 7200 RPM 9G IBM SCSI drive there lately, and a Quantum simply would not stack up to that (5.5ms avg access). Regards, Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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