Milliseconds spent writing This is the total number of milliseconds spent by all writes (as measured from __make_request() to end_that_request_last()). Milliseconds spent reading This is the total number of milliseconds spent by all reads (as measured from __make_request() to end_that_request_last()). Writes merged Writes which are adjacent to each other may be merged for efficiency. Thus two 4K reads may become one 8K read before it is ultimately handed to the disk, and so it will be counted (and queued) as only one I/O. This field lets you know how often this was done. I/Os currently in progress The only field that should go to zero. Incremented as requests are given to appropriate struct request_queue and decremented as they finish. Reads completed This is the total number of reads completed successfully. Writes completed This is the total number of writes completed successfully. Reads merged Reads which are adjacent to each other may be merged for efficiency. Thus two 4K reads may become one 8K read before it is ultimately handed to the disk, and so it will be counted (and queued) as only one I/O. This field lets you know how often this was done. Weighted # of milliseconds spent doing I/Os This field is incremented at each I/O start, I/O completion, I/O merge, or read of these stats by the number of I/Os in progress (ios_in_progress) times the number of milliseconds spent doing I/O since the last update of this field. This can provide an easy measure of both I/O completion time and the backlog that may be accumulating. Sectors written This is the total number of sectors written successfully. Sectors read This is the total number of sectors read successfully. Milliseconds spent doing I/Os This field increases so long as field ios_in_progress is nonzero