Date: Mon, 08 Sep 1997 15:05:39 +1000 From: Mike Smith <mike@smith.net.au> To: Greg Lehey <grog@lemis.com> Cc: Mike Smith <mike@smith.net.au>, Simon Shapiro <Shimon@i-connect.net>, FreeBSD Chat <chat@freebsd.org> Subject: Re: lousy disk perf. under cpu load (was IDE vs SCSI) Message-ID: <199709080505.PAA01452@word.smith.net.au> In-Reply-To: Your message of "Mon, 08 Sep 1997 14:58:37 %2B0930." <19970908145837.07934@lemis.com>
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> > > > However, Simon is close; the ESMD spec allows for a data clock of 25MHz > > (the data separator is on the disk, not the controller, IIRC). > > Depends on the drive. What "depends" on the drive? The ESMD spec lays out the maximum clock rate for the data, and the separator has to be on the drive if you're going to claim to be ESMD. > > The later ESMD disks were pretty hot performance-wise (eg. the > > Fujitsu Super Eagle and its successorss), > > Sure, but they weren't exactly the kind of drive built in the > mid-70s. The 3330 was the "standard" drive, and it had 30 sectors per > track, 3600 rpm. How many kB/s do you get out of that? How many heads are you reading in parallel? I've had blood out of similar units on my hands (and blood out of my hands on similar units 8) and I get the distinct impression that multiple-head read activity was the norm. > > Yup. And if someone can work out how to deal with the power > > dissipation, a slab of pseudo-static RAM the size of a 3.5" drive will > > probably be cost-comparable inside the next 5-10 years. > > Assuming the disk drive people don't continue to improve their > devices. Round about the time of the last anecdote (early 80s), the > head of Tandem's HPRC said something to the effect that we needn't > worry too much about disks, because they would die out in the next 10 > years, considering the way the price of RAM was dropping. Sure. I think your earlier point about the basic mechanical limitations is quite valid though; there's a basic restriction inherent in having to fling the head assembly around. Still... mike
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