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Topics: [fun][zfs]

Учёт лево-крутящихся дисков в Южном полушарии в ZFS

https://github.com/openzfs/zfs/pull/11823
Патч меридиональных дисков:

    * Some minor math equations need to be solved. But it should help
      protect data for our southern most users.
    * This will future-proof ZFS against Earth's expected
      magnetic-pole-reversal
    * SMR disks untested
    * Looking for testers at the extreme poles
    * Using dst testing might violate GPL

    Motivation and Context

        ZFS needs to take into effect F = d/dt * (mv) and possibly
        Eötvös effect.

    How Has This Been Tested?

        Extensive testing. To simulate southern hemisphere disk arrays
        were held by the Testing&Integrity Team Members and "spun really
        fast" in the opposite direction.

    chrisrd commented Apr 1, 2021
        Please make this configurable on a per-disk basis: we
        specifically use right-spinning disks right now, but we'd like
        to gradually replace them with left-spinners if possible as the
        right-spinners use more power due to the negative coriolis
        effect down here.

    bghira commented Apr 1, 2021
        the test failures are caused by not taking into account that the
        disks can be mounted vertically. in the test failures, the disk
        is told to move left but this is actually 'down' and the right
        rotation should be mapped to 'up' and reverse this for mounting
        in opposing direction.

    adamdmoss commented Apr 1, 2021
        FWIW I gave this a spin; didn't notice any difference in my
        casual testing, but I should note that my disk array sits
        precisely on the equator.

    debdrup commented Apr 1, 2021
            Please make this configurable on a per-disk basis: [...]
        Another use for per-disk configuration is if you've got one disk
        in Australia and another in Denmark.

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