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I was studying about the activity/change while copy pasting file in USB. Seems like the stat attribute gets changed on every action on USB drive. So what does each value of these stat denotes?

Command used:

udevadm info --attribute-walk --name=sdb1

A Part of output:

ATTRS{stat}=="     263    14879    17884     1145      559      122   126280
      10082        0     2892     9348        0        0        0        0"

What are the meaning of each values of ATTRS{stat}? Any links to documentation will also be helpful.

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For a block device, the stat udev attribute shows the device’s statistics, which can also be seen in the corresponding entry under /sys/devices (udevadm info will show the full path) and under /sys/block (/sys/block/sdb/sdb1/stat in your example).

The entries can be seen in block/genhd.c and are documented in the kernel; they are, in order:

  • number of read I/Os processed
  • number of read I/Os merged with in-queue I/O
  • number of sectors read
  • total wait time for read requests (in milliseconds)
  • number of write I/Os processed
  • number of write I/Os merged with in-queue I/O
  • number of sectors written
  • total wait time for write requests (in milliseconds)
  • number of I/Os currently in flight
  • total time this block device has been active (in milliseconds)
  • total wait time for all requests (in milliseconds)
  • number of discard I/Os processed
  • number of discard I/Os merged with in-queue I/O
  • number of sectors discarded
  • total wait time for discard requests (in milliseconds)
  • number of flush I/Os processed
  • total wait time for flush requests (in milliseconds)
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  • Thank you @Stephen for the answer. Another thing, Is there a way to determine how many MB of data is transferred to USB using udev or so?
    – PaxPrz
    Nov 6, 2020 at 9:30
  • I don’t know off-hand, it would be worth asking a separate question. Nov 6, 2020 at 9:37

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