What does "I/O Reads or Writes" and "I/O Read Bytes or Write Bytes" mean?

Question

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?

Solution

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.

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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

Comments

[Ramhound]

Why is the title "I/O Read (Write) Bytes" but in the question you simply say its "I/O Read Bytes"?

[DavidPostill]

"I/O Reads" number is number of reads, "I/O Writes" is number of writes, "I/O Read Bytes" is total bytes read and "I/O Write Bytes is total bytes written. One read or write will transer many bytes at once.

[skr3am]

@DavidPostill, have you read the entire question before commenting? I understand that "I/O Reads" number is number of reads, no need to get all captain obvious on me. Can you explain to me how is it possible that I have a process with e.g. 4 MiB "I/O Read Bytes" and zero "Disk Read Bytes"?

[skr3am]

@Ramhound, I simply wanted to make the title shorter.

[Ramhound]

Be nice to David, we get lots of people with different skill levels, your question is confusing we are doing our best

[DavidPostill]

@skr3am See my answer.