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    SubjectRe: Benefits from computing physical IDE disk geometry?
    Nick Piggin wrote:


    >>
    >> Any good SCSI drive knows the physical geometry of the disk and can
    >> therefore optimally schedule reads and writes. Although necessary features,
    >> like read queueing, are also available in the current SATA spec, I'm not
    >> sure most drives will implement it, at least not very well.
    >>
    > The "continuous" nature of drive addressing means that the kernel
    > can do a fine job seek-wise. Due to write caches and read track
    > buffers, rotational scheduling (which could be done if we knew
    > geometry) would provide too little gain for the complexity. I would
    > say that for most workloads you wouldn't see any difference. (IMO)


    OTOH you can come up with scenarios like, say, a DBMS doing 16K page
    aligned IO to raw devices where you might see big gains from making sure
    those 16K chunks didn't cross a physical cylinder boundary.


    --
    Chuck
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