Windows – What does “I/O Reads or Writes” and “I/O Read Bytes or Write Bytes” mean

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In Task Manager (and Sysinternals' Process Explorer) there are columns called "I/O Reads", "I/O Writes", "I/O Read Bytes" and "I/O Write Bytes". So what do these counters mean exactly? What else, besides disk and network activity, do they include?

In Process Explorer I see a number of processes which have zero "Disk Read Bytes" and "Network Receive Bytes", but a non-zero "I/O Read Bytes". And conversely, some processes have a "Disk Read Bytes" value larger than "I/O Read Bytes". How is this possible?

Best Answer

How is it possible that I have a process with 4 MiB "I/O Read Bytes" and zero "Disk Read Bytes"?

I/O Read Bytes is more than just Disk Read Bytes:

  • It includes File, Network and Device I/O
  • It does not include Console I/O

I/O Read Bytes - The number of bytes read in input/output operations generated by a process, including file, network, and device I/Os. I/O Read Bytes directed to CONSOLE (console input object) handles are not counted.


What does I/O data mean?

I/O Columns of Process Explorer

  • I/O Delta - The change in I/O operations since the last measurement

  • I/O Delta Bytes - The change in I/O bytes since the last measurement.

  • I/O Other - The number of input/output operations generated by a process that are neither reads nor writes, including file, network, and device I/Os. An example of this type of operation would be a control function. I/O Others directed to CONSOLE (console input object) handles are not counted.

  • I/O Other Bytes - The number of bytes transferred in input/output operations generated by a process that are neither reads nor writes, including file, network, and device I/Os. An example of this type of operation would be a control function. I/O Other Bytes directed to CONSOLE (console input object) handles are not counted.

  • I/O Read Bytes - The number of bytes read in input/output operations generated by a process, including file, network, and device I/Os. I/O Read Bytes directed to CONSOLE (console input object) handles are not counted.

  • I/O Reads - The number of read input/output operations generated by a process, including file, network, and device I/Os. I/O Reads directed to CONSOLE (console input object) handles are not counted.

  • I/O Write Bytes - The number of bytes written in input/output operations generated by a process, including file, network, and device I/Os. I/O Write Bytes directed to CONSOLE (console input object) handles are not counted.

  • I/O Writes - The number of write input/output operations generated by a process, including file, network, and device I/Os. I/O Writes directed to CONSOLE (console input object) handles are not counted.

Source Trying to understand Process Explorer's I/O data

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