back to article Disk platter sizes vary with drive speeds

When is a 2.5-inch form factor drive not a 2.5-inch form factor drive? A small form factor (SFF) drive comes in an industry standard 2.5-inch form factor case size. Inside that there can be one or two platters and which can be smaller or larger. Yes, they will be smaller platters than ones found in 3.5-inch form factor cases, …


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  1. SuperTim

    And the moral is....

    That platter size doesnt matter a jot, only performance statistics.

    Who cares how big the platter sizes are? it doesnt make any different at all, as you never see them or have to accommodate them. They are built into the form factor of the drive and for all i care , the case could be 99% empty as long as the drive performs as promised.

    Have you ever looked inside a midi system? there is nothing inside..... but they still made them that way because people want a certain size of product. As PCs have 3.5 inch bays, thats how big the HDD cases are, but the guts dont need to adhere to that size.

    It's all irrelevent anyway as we will all soon be using some more modern technology that the venerable spinning media. Hell, there is probably some "magic" drive hanging about seagate or hitachi, but they want to offload their old fashioned magnetic media for another few years yet!

  2. Jan Silver badge
    Dead Vulture

    In other news...

    In other news: The sun rose today.

    tombstone... It really should not have been neccessary to explain this in first place.

  3. Alex Wright

    Ummm? Stating the obvious?

    No Comment.

  4. lasersage

    surely GB not MB

    A SFF Momentus 7900 might have 250MB/platter while the SFF Savvio 15K.2 has 148MB

    This can't be right, I can fit more on a CD

  5. Anonymous Coward
    Paris Hilton

    And so it has been for years.

    Platter sizes have varied according to rotational speed for a number of years now, it's not news and it always brings a smile when i hear the anoraks debating hard disk drive performance.

    Paris, A couple of platters short.

  6. Anonymous Coward
    Anonymous Coward

    Per Sq Inch

    Why not just quote densities as per sq inch rather than platter?

  7. Mike Kamermans

    Was this an article?

    Colloquial speech is colloquial...

  8. Trygve Henriksen
    Thumb Down


    Why not drag the old Quantuum Bigfoot 5.25" drives into this, too?

    (From the late 90s, I think)

    Anyone remembers that piece of cheap sh!te?

    Cheap, big, slow, noisy...

    Might as well start talking Iomega Bernoully, Jaz, Zip, Clik!...

  9. Anonymous Coward
    Anonymous Coward

    You stored data on spinning glass platters?

    In 20 years time, kids are going to laugh at the idea that we stored data on spinning platters of glass.

  10. Dave Silver badge
    Dead Vulture


    Surprisingly enough, manufacturers generally _do_ quote areal density (as they like to call it) as values per square inch.

    Only the losers play around with terms like platter density...

    And no-one buys drives based on either value.

  11. Pete

    Also, you children may not know

    the platters inside are axually round like a circle - EVEN though the outer case is sorta rectangiller (Texan drawl)

    Next week can we learn about the alphabit or numbas?

  12. Chris Mellor


    Sent tome by mail: "Faster spin drives are also designed for short seeks to optimize access times - hence smaller platters."

  13. Dazed and Confused Silver badge


    OK so it's been a few years since I bothered to look at these but I found that the data densities on so called high performance (15K rpm) disks were often lower than those on slow 10K or 7.2K drives. If you compared the maximum transfer speeds of the drives they were the same. This implies that the bandwidth of the analogue parts of the electronics were to some extent limiting the used data densities. Generally server users don't care too much about the transfer speed, they are interested in the transaction rate for random IO, so they're not too fussed about this.

  14. Graham Marsden

    Areal density?

    Are they from Brisle?

    (For those who aren't aware, the Bristol accent tends to add an "L" sound on the end of words, hence "Eval Turnel, Primal Donnal of the Carl Rosal Operal")

  15. Anonymous Coward

    how does this relate to my 8 inch floppy

    No, it's not a personal problem, but it could be if I let it....

  16. James O'Brien

    @ Trygve Henriksen

    Funny you ask about the Bigfoot.....

    I have one of them on my wall here at work thing probably still works (I stress probably here) but I dont really want to test it in one of my systems.

    5.25" and 8Gb total how times have changed

  17. Anonymous Coward
    Anonymous Coward


    a news site for geeks with an article so anally retentive as to make the readership look normal.

  18. Anonymous Coward
    Anonymous Coward

    We Know ...

    That fast platter rotation = higher data density per cm2.

    This has always been known -- as long as disk storage has existed.

  19. Jeffrey Nonken


    Yeah, I've got a couple of those Bigfoot drives in storage.

    And some 8" floppies.

    Me, I'd rather have a 5 1/4 inch hard one than an 8 inch floppy one.

  20. Slackness
    Thumb Down

    and for my next report

    The variable nature of variables, and why....

    Jeez that was a pile of 'oh-christ-its-near-friday-must-produce-some-old-shite'.


  21. Anonymous Coward

    @Jeffrey Nonken

    I never heard of 5 1/4 hard ones...only the 3.5 inchers, but the only one i ever had i was only a year old. I found the 8's still work just fine in the right drive.

  22. Nigel

    Another meaningless indicator

    Areal density is for disk drives, what Megahertz was for processors. Certainly , it is a measure of how far the product has advanced along one of the many possible axes of technological progress. But as far as measuring the utility of the product to the end user goes, it is meaningless.

    I expect that the expensive fast small-platter high-RPM drives will be the first to get obsoleted by SSDs, in the very near future. It'll take much longer for SSDs to catch up with big slower cheap multi-terabyte hard disks (2Tb for £200 today means 2Tb for £50 three years hence). Maybe they never will. If hard drive manufacturers can work out how to squeeze tracks much closer together, the data density of magnetic HDDs will forever stay ahead of SSDs, based on the physics.

    If we ever get them, what will we do with 100Tb disk drives?

    5.25" full height hard drives? That wasn't where they started. A real old-timer can remember old "Winchester" technology hard drives. (Also eight-inch floppies). The HDA was about 15 inches across, stored in a unit the size of a dishwasher. Disk capacity? 80Mb. Yes, MB, not Gb. Before then the HDA was not sealed and the disks were in removeable cartridges. I've still got a platter extracted from one of those that was being scrapped. Diameter, about 15 inches. Capacity, just over one Megabyte.That's what was used before floppy disks were invented!

  23. Anonymous Coward


    Reminds me of some old glass platters for optical writing we used to use.....

    But nothing beats those old flying head drums we had....aye carumba!

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