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Systemd/Microsoft Effort For A Global Counter On Block/Disk Changes Coming To Linux 5.15

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  • #21
    Originally posted by MadeUpName View Post
    Is there a use case where this would be preferable to looking at the SMART data which is actually stored on the disk?
    Every use case, because these are completely different things.

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    • #22
      IBM/Microsoft/Systemd/Linux

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      • #23
        Let systemD/Microsoft fanboys get rekted. On my personal machine I WILL use GNU/Linux however I please with no systemD/Microsoft engineered components. I gave up trying to prove my point a long time ago, I'm just sitting here with popcorn watching some people with brains starting to reconsider things, like using non-systemD distros for personal usage.
        I've been Poettering-free since this whole fiasco began and I guarantee you this; everything you guys do with systemD I do it too with simple scripts and small programs, I'm as productive as ever without a care in the world knowing my system is 50% more secure without Poettering/Microsoft ware.

        I won't reply to your inane comments.

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        • #24
          It's a bit amusing to read these news, because someone usually pops up to tell you how you could already do whatever thing that systemd (though often misspelling/miscapitalizing that word) is introducing - or helped create, usually linking some 20k line bash monstrosity that technically can do the same thing if all the stars align and your hardware was made by the absolute highest bidder.

          Honestly, I tried to do physical disk discovery myself at one point, but - at least on SATA - it's basically impossible to uniquely identify a physical drive. Manufacturers apparently do everything to not have to spend even a cent more to - for instance - burn the required IDs correctly into the firmware.
          And don't get me started on SPD in DDR RAM. I've got a bunch of DDR3L sticks in different sizes and from different manufacturers that - according to themselves - apparently were produced in the same factory, at the same time, in the same batch, with the same unique identifier, by the same manufacturer.

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          • #25
            Can someone actually clarify wtf this is? Is it an on-disk number? Or a counter that starts at zero when a device is mounted and incremented when it's touched? If the latter, why does microsoft need to be involved? Not a very clear explanation in the article.

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            • #26
              Originally posted by Developer12 View Post
              Can someone actually clarify wtf this is? Is it an on-disk number? Or a counter that starts at zero when a device is mounted and incremented when it's touched? If the latter, why does microsoft need to be involved? Not a very clear explanation in the article.
              It's a number that refers to a particular disk, and only ever to that particular disk.

              Plug a disk in, it becomes 0 - and all applications that track disks can know that they're talking to disk 0, the next is 1, then 2, etc. None of the sd[whatever letter happened to be available at the time] stuff that can cause a new disk to suddenly occupy a name that referred to another disk earlier.

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              • #27
                Originally posted by Ananace View Post

                It's a number that refers to a particular disk, and only ever to that particular disk.

                Plug a disk in, it becomes 0 - and all applications that track disks can know that they're talking to disk 0, the next is 1, then 2, etc. None of the sd[whatever letter happened to be available at the time] stuff that can cause a new disk to suddenly occupy a name that referred to another disk earlier.
                Is this number stored on-disk? Why does microsoft have to be involved?

                If I understand you right, numbers map to disks and the one-to-one number<->disk mapping never changes, correct? (not incrementing with each operation done to the disk, like a sequence number)

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                • #28
                  Originally posted by Developer12 View Post

                  Is this number stored on-disk? Why does microsoft have to be involved?

                  If I understand you right, numbers map to disks and the one-to-one number<->disk mapping never changes, correct? (not incrementing with each operation done to the disk, like a sequence number)
                  The number is just something that the kernel tracks, so it's only stored as a memory value during runtime.
                  Guessing that Microsoft has had issues with correctly handling hot mounting of storage while under load in either WSL or Azure, and they want something to improve it kernel side.

                  The number would probably change if you were to unplug the drive and then plug it back in again, as - at that point - it'd be a new disk attached to the same system.

                  As I understand it, this is just to make sure that when your application is set to use disk X, then it will only ever actually access disk X, never accidentally disk Y if something happens to swap them around - due to something like a USB hub resetting.

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                  • #29
                    Originally posted by Developer12 View Post

                    Is this number stored on-disk?

                    If I understand you right, numbers map to disks and the one-to-one number<->disk mapping never changes, correct? (not incrementing with each operation done to the disk, like a sequence number)
                    Imagine to have an usb disk named /dev/sdd. You unplug and replug it, how can an application know that /dev/sdd is the same as 10 minutes ago?
                    The number now increases for every disk registration, and it's unique since boot:


                    [email protected]:~# cat /sys/block/sdd/diskseq
                    7
                    [email protected]:~# cat /sys/block/sdd/diskseq
                    10

                    Originally posted by Developer12 View Post
                    Why does microsoft have to be involved?
                    What we should do when finding an issue? Waiting for others to solve?

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                    • #30
                      Originally posted by teknoraver View Post
                      when finding an issue? Waiting for others to solve?
                      I was wondering if this was going to become a cross-OS on-disk standard for (re-)identifying disks.

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