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    SubjectRe: [PATCH] Configure IDE probe delays
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    On Wed, 2004-09-01 at 11:06, Alan Cox wrote:
    > On Mer, 2004-09-01 at 14:20, Mark Lord wrote:
    > > LBA48 is only needed when (1) the sector count is greater than 256,
    > > and/or (2) the ending sector number >= (1<<28).
    >
    > I've played with this a bit and in the -ac IDE code it can drop back
    > to LBA28 for devices that are small enough not to need LBA48 when the
    > controller only supports PIO for LBA48 modes (eg some ALi) as 2.4-ac
    > did.
    >
    > > I regularly include this optimisation in the drivers I have been
    > > working on since LBA48 first appeared.
    >
    > It isn't always a win. You get cut down to 256 sectors per I/O which for
    > some workloads has a cost and you need to factor that into the command
    > issue choice as well as the last sector number being accessed.
    >

    I have never been able to measure a decrease in disk throughput in any
    disk benchmark with 256 sectors per I/O vs. 1024. This is a modestly
    powered desktop with a single drive though. What kinds of workloads
    would you expect to be affected by this?

    Lee

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