https://www.kernel.org/doc/Documentation/ABI/testing/procfs-diskstats What: /proc/diskstats Date: February 2008 Contact: Jerome Marchand Description: The /proc/diskstats file displays the I/O statistics of block devices. Each line contains the following 14 fields: == =================================== 1 major number 2 minor mumber 3 device name 4 reads completed successfully 5 reads merged 6 sectors read 7 time spent reading (ms) 8 writes completed 9 writes merged 10 sectors written 11 time spent writing (ms) 12 I/Os currently in progress 13 time spent doing I/Os (ms) 14 weighted time spent doing I/Os (ms) == =================================== Kernel 4.18+ appends four more fields for discard tracking putting the total at 18: == =================================== 15 discards completed successfully 16 discards merged 17 sectors discarded 18 time spent discarding == =================================== Kernel 5.5+ appends two more fields for flush requests: == ===================================== 19 flush requests completed successfully 20 time spent flushing == ===================================== For more details refer to Documentation/admin-guide/iostats.rst