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    SubjectRe: ATA 4 KiB sector issues.
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    >>>>> "James" == James Bottomley <James.Bottomley@suse.de> writes:

    James> However, for 4k sectors, the main issues which have shown up in
    James> testing by others (mostly Martin) are

    James> 1. In native 4k mode, we work perfectly fine. *however*,
    James> most BIOSs can't boot native 4k drives.

    Correct. I have engaged with pretty much all the big OEMs in the
    industry and so far the interest has been near zero.


    James> 4. The aligment problem is made more complex by drives that
    James> make use of the offset exponent feature (what you refer
    James> to as offset by one) ... fortunately very few of these
    James> have been seen in the wild and we're hopeful they can be
    James> shot before they breed.

    This topic is constantly up for debate in IDEMA. However, it looks like
    we might win because of the impending demise of XP.


    James> so the bottom line seems to be that if you want the device as a
    James> non boot disk, use native 4k sectors and a non-msdos partition
    James> label. If you want to boot from the drive and your bios won't
    James> book 4k natively, partition everything using the 512 emulation
    James> and try to align the partitions correctly. If your bios/uefi
    James> will boot 4k natively, just use it and whatever partition label
    James> the bios/uefi supports.

    James> Martin can fill in the pieces I've left out.

    Here's my latest take given what I hear on the grapevine:

    1. 512-byte logical block size drives will be around forever for legacy
    deployments because nobody is willing to do the required BIOS int13
    work. It's not just a BIOS thing, this requires heavy changes to HBA
    boot ROMs as well.

    2. Some vendors are working on EFI firmware and will support booting off
    of 4KB LBS drives there. This is mostly aimed at the server space.

    3. 4 KB logical block size drives will mainly be targeted for use inside
    arrays. Off the shelf enterprise drive models will most likely
    continue to ship with a 512-byte LBS.

    4. Part of the hesitation to work on booting off of 4 KB lbs drives is
    motivated by a general trend in the industry to move boot
    functionality to SSD. There are 4 KB LBS SSDs out there but in
    general the industry is sticking to ATA for local boot.

    --
    Martin K. Petersen Oracle Linux Engineering


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