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    SubjectAW: Need to force IDE geometry
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    Hi Andries,

    > Your question is based on your assumptions about geometry
    > and LBA. But your assumptions are incorrect, and therefore
    > your questions do not make sense. Please tell what you do
    > and what error messages you get.

    For some reasons the c/h/s settings reported for LBA disks depend on ide device number: /hda uses 255 heads, 63 sectors while /dev/hdc and above use 16 head, 63 sectors.

    hda: 150136560 sectors (76870 MB) w/1916KiB Cache, CHS=9345/255/63, UDMA(33)
    hdb: 150136560 sectors (76870 MB) w/1916KiB Cache, CHS=148945/16/63, UDMA(33)
    hdc: 150136560 sectors (76870 MB) w/1916KiB Cache, CHS=148945/16/63, UDMA(33)

    As you can see, this means you end up with different reported drive geometries for identical disks. Esp. if you want to use software raid this is a major nuisance. The usual workaround is to change head/cylinder settings when first partitioning the drive and let linux change the geometry during partition table check.

    Partition check:
    hda: hda1 hda2 < hda5 hda6 > hda3
    hdb: [PTBL] [9345/255/63] hdb1 hdb2 < hdb5 hdb6 > hdb3
    hdc: [PTBL] [9345/255/63] hdc1 hdc2 < hdc5 hdc6 > hdc3

    While this works, it's quite unintuitive and confusing; correct behaviour would be to treat all disks identicaly regardless of device number.

    Bye, Martin
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