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    SubjectRe: defrag deployment status (was Re: [PATCH] ext4: allow defrag (EXT4_IOC_MOVE_EXT) in 32bit compat mode)
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    On Mon, Mar 8, 2010 at 11:22 AM, jim owens <owens6336@gmail.com> wrote:
    > David Newall wrote:
    >> Christian Borntraeger wrote:
    >>> Some bigger things are missing in the e4defrag tool:
    >>> ...
    >>> - overall layout considerations (e.g. putting files close to its
    >>> directory or
    >>>   use the atime to move often used files to the beginning of a disk etc.)
    >>
    >> Shouldn't oft-used files be placed closer to the middle?  If you place
    >> them at the beginning of the file, it's only possible for the head-stack
    >> to be close to the file from the inner direction.  Place them in the
    >> middle and it's possible for the head-stack to be close from the outer
    >> direction, too, which sounds like a doubling of probability.  It seems
    >> that it's the least frequently used files that should be placed at one
    >> end of the disk or the other.
    >
    > No.  Your logic would be correct if rotating disks had
    > similar speed at all locations.  Current disks are much
    > faster at the 0 end than at the middle or highest address.
    >
    > It is not unusual to see 2x difference in transfer speed
    > so you always want the important stuff as low as possible.
    >
    > jim

    Jim, I should know this, but is sector 0 on the outside edge, or the inner edge?

    I assume outer so that the linear speed of the platter under the head
    is faster and thus more data per second is passing under the head.

    Greg
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