Date: Thu, 2 May 1996 02:55:41 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: terry@lambert.org (Terry Lambert) Cc: luigi@labinfo.iet.unipi.it, terry@lambert.org, msmith@atrad.adelaide.edu.au, koshy@india.hp.com, hackers@FreeBSD.ORG, current@FreeBSD.ORG Subject: Re: lmbench IDE anomaly Message-ID: <199605020755.CAA00185@dyson.iquest.net> In-Reply-To: <199605020128.SAA10906@phaeton.artisoft.com> from "Terry Lambert" at May 1, 96 06:28:40 pm
next in thread | previous in thread | raw e-mail | index | archive | help
> > > Anyway, the results showing SCSI being better than IDE are certainly > > > valid. > > > > So we are back to the regular "SCSI is better than IDE" debate... > > "Better" as in a "lower system overhead unless you've written a PIO4 > EIDE driver that you haven't shared with the rest of us and overcome > the interrupt bugs in 3 out of the 4 most popular IDE controller > chipsets and overcome the PIO4 probe crashing non-PIO4 systems and > even then, the DMA overhead is slightly higher than SCSI and EIDE > CDROM's use SCSI commands over the IDE interface anyway" kind of way. > > Purely "subjective". ;-). > > On FreeBSD, as long as your bios (at least on my ASUS TPN motherboard) sets the drive mode to a good one, you get the advantage of the PIO mode that the bios senses. On my new 2.5GByte WD Caviar, I get 8-9MBytes read perf on FreeBSD. I have been looking at implementing DMA using Garrett's IDE dma code, but haven't gotten to it yet. The WD type drives don't/can't take advantage of things like tagged queuing, and the 2.5Gbyte drive that I have only has a 128K cache. But, I'll put my 200usec or so command overhead against any AHA2940/Atlas drive anytime. In some ways, the EIDEs are pretty impressive. Bottom line, the EIDE drives do appear to be slower in many if not most respects than a very good SCSI drive, but my 2.5Gbyte Caviar is almost always faster than my 2Gbyte SCSI Hawk. (With perhaps a little more overhead -- but maybe not.) With the 2.5Gbyte Caviar's being about $400US in wholesale, with no SCSI adapter needed, they are probably pretty darned good price/perf for workstation use. John
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199605020755.CAA00185>