Date: Tue, 9 Sep 1997 22:57:33 +0200 From: Stefan Esser <se@FreeBSD.ORG> To: Terry Lambert <tlambert@primenet.com> Cc: Mats Lofkvist <mal@algonet.se>, current@FreeBSD.ORG Subject: Re: lousy disk perf. under cpu load (was IDE vs SCSI) Message-ID: <19970909225733.44758@mi.uni-koeln.de> In-Reply-To: <199709090206.TAA00939@usr07.primenet.com>; from Terry Lambert on Tue, Sep 09, 1997 at 02:06:08AM %2B0000 References: <199709082256.AAA04008@kairos> <199709090206.TAA00939@usr07.primenet.com>
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On Sep 9, Terry Lambert <tlambert@primenet.com> wrote: > > 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. Ahemm, the NCR driver was the first SCSI driver in FreeBSD that handled tagged commands, back in, well, it existed in the driver kit for FreeBSD-1.1.x as of spring 1994 ... > 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. Ahemm, you are sure you got a 53c810b ??? Those were never built, AFAIK ;-) The 53c810 was the original NCR SCSI chip. It has been replaced by the 53c810a (which shares the PCI ID with the 53c810, but with a revision ID >= 0x10). The "a" version offers the same features as the 53c860, except for Fast-20 support. > 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). Hmmm, you must have performed the tests on a file system, that covered only a small fraction of the disk. Random seeks will then cover only a small range of cylinders, and in the case of a file system in the outer area, 1GB of 9GB may restrict seeks to 1/15 to 1/20 of the tracks (because of the larger capacity of outer tracks) ... The IBM DCHS (I assume you were testing one of those) is about as fast as a Quantum Atlas II, which has just recently been sold out at near EIDE prices, since the Atlas III will take its place as the server disk offering of Quantum. (And the Atlas III should give you 10MB/s on the inner tracks, and up to 16MB/s on the outer tracks, if I interpret the data sheets on Quantums web site correctly ...) Regards, STefan
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