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    SubjectRe: File system compression, not at the block layer
    On Sat, Apr 24, 2004 at 11:05:05PM -0400, Horst von Brand wrote:

    > > Haven't you noticed that drives with many
    > > platters are always faster than their cousins with fewer platters ? And
    > > I don't speak about access time, but about sequential reads.
    > Have you ever wondered how they squeeze 16 or more platters into that slim
    > enclosure? If you take them apart, the question evaporates: There are 2 or
    > 3 platters in them, no more. The "many platters" are an artifact of BIOS'
    > "disk geometry" description.

    I know, I was speaking about physical platters of course. Mark Hann told
    me in private that he disagreed with me, so I checked recent disks
    (36, 73, 147 GB SCSI with 1, 2, 4 platters) and he was right, they have
    exactly the same spec concerning speed. But I said that I remember the
    times when I regularly did this test on disks that I was integrating about
    7-8 years ago, they were 2.1, 4.3, 6.4 GB (1,2,3 platters), and I'm fairly
    certain that the 1-platter performed at about 5 MB/s while the 6.4 was around
    12 MB/s. BTW, the 9GB SCSI I have in my PC does about 28 MB/s for 1 platter,
    while its 18 GB equivalent (2 platters) does about 51. So I think that what
    I observed remained true for such capacities, but changed on bigger disks
    because of mechanical constraints. Afterall, what's 18 GB now ? Less than
    one twentieth of the biggest disk.

    Anyway, this is off-topic, so that's my last post on LKML on the subject.

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