QUANTUM Message Board - Msg: 3460556

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Technology Stocks : QUANTUM

QNTM 9.380

-4.7%

Dec 12 9:30 AM EST

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To: John Biddle who wrote (7366)	2/18/1998 8:43:00 AM
From: UpwardBound	of 9124

Re: dual actuators in disk drives John, In the case where an application needs double the throughput, there is such a thing as synchronized spindles. This had been applied for years at Seagate. I'm not sure if they are still doing it. What happens is two drives are synchronized and then the data is interleaved between the two, doubling the burst transfer rate. This of course requires a much modified controller, but at least the drives are basically off the shelf units (sync spindle is fairly simple to do) and there's no redundant hardware. If an application needs blazingly high speed, they have also built drives that have parallel read channels where they read from multiple heads simultaneously. Again, Seagate has also done this, but I can't say if it's still going on. At one point they were shipping an 8" product that offered 2 heads parallel and another version of that with 9 heads parallel (8 data bits with one parity). The 9 head parallel was a specialty product developed jointly with supercomputer manufacturer Cray. Very early in the disk drive industry I heard that IBM(?) had built a 14" product that had dual actuators but that did not last long. Also going way back, IBM also manufactured a 14" product (MMD) that had a large number of fixed heads on one side of a disk. (I think this product ended up being transferred to Control Data as part of the settlement of some sort of lawsuit.) This product had a PCB with something like 50 heads mounted on it and then a rotating disk that just sat on top. TPI was very low back then and thermal expansion was never an issue like it is today. That's why we have embedded servo. Probably more than you wanted to know. Anyway, since the things you are suggesting have been implemented in the past, you should be pleased to know that your ideas have merit. Take Care, --UpwardBound

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