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warmonger

"Big" hard drives

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I was installing a wireless network for a friend when I noticed that he had a big ol' 5.25" hard drive installed (though not being used). This got me thinking about something. Why are hard drives using 3.5" now? If they aren't using the same platter size, then the bigger drives could store much more data on them per platter. Of course, if they used to use the same size platters on the old drives, then there's really no difference. But anyway, are there any practical reasons for the smaller drives nowadays?

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I was installing a wireless network for a friend when I noticed that he had a big ol' 5.25" hard drive installed (though not being used). This got me thinking about something. Why are hard drives using 3.5" now? If they aren't using the same platter size, then the bigger drives could store much more data on them per platter. Of course, if they used to use the same size platters on the old drives, then there's really no difference. But anyway, are there any practical reasons for the smaller drives nowadays?

The media fab places no longer have equipment for producing and inspecting 5.25 inch media. It would require a significant amount of capital to tool up to support it again. Similarly, the motor vendors and other component makers would have to retool and/or lose efficiency in their factories because they'd have to deal with bigger parts. Lastly, each of the HDD makers would also have to retool their assembly tools/fixtures, packing boxes, etc., to handle larger drives.

It really all comes down to economics. There is no technological reason such a drive couldn't be designed, AFAIK.

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The most recent incarnation of 5.25" hard drives were the Quantum Bigfoot and every body hated them for their slow access times.

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The most recent incarnation of 5.25" hard drives were the Quantum Bigfoot and every body hated them for their slow access times.

That's pretty much it.

The problem is two-fold. One, the wider disc means longer moving the head from one end to another. Two, the larger platter means slower rotational speeds. (Just like moving from 7200 RPM to 10,000 RPM to 15,000 RPM reduces the size of the platter, to get BIGGER platters, you must slow it down.)

While I think a one terabyte drive at 5400 RPM would be nice, (probably even more, since a 5.25" disk more than doubles the area of a 3.5" disk, 21.6 sq. in. vs. 9.6 sq. in., and you could probably have more than 4 platters,) it's just not worth it at this point.

Heh, the Seagate ST423451W SCSI drive was a 23GB SCSI drive, with 14 platters, spun at 5400 RPM, at 125.3 kbits per inch, of course, it's a 5.25", FULL HEIGHT drive (full height means the height of two CD-ROM drives.) The X15.3, on the other hand, at 18.1GB, has one platter, spins at 15,000 RPM, and packs in 533 kbits per inch. The 5.25" drive has a whopping 28.2ms full seek time, whereas the 15k drive has a measly 6.7ms full seek time.

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It's actually worse than that (you only mentioned the major problems:)

Bigger platters = more mass = bigger motors = higher current draw = more heat = less reliability

Bigger platters = more torque = easier to damage by dropping or vibrating = less reliability

I'd love bigger HDDs too! I would gladly trade double the capacity for half the performance (access time *AND* STR even). I'd go the other way too. 15K SCSI runs up to 73GB. 18G is way more than I need for a boot drive and other frequently-used data, so that would get me a drive 4x as fast. That would be a speed jump you could definately feel!

Also, terabyte drives would only have to be about 7x slower than the new 10K.6s. That would drop you way back to 5-10MB/sec transfer rate, so it would take 30-40 hours to fill though. Even so, a terabyte drive for $800 would be nice. I've got room *right* over here for a 5-drive RAID5 array with a hot-spare. I do believe 4TB would last me a goodly long time. Of course, I said the same thing about 40MB, 400MB, 20GB, and 325GB and at every jump I filled the space in less time than the previous one...

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