Use iotop (thanks Guillaume Chazarain) to figure out (thanks Paul Wise) where the issue is at.
iotop(1) – Linux man page
iotop – simple top-like I/O monitor
iotop watches I/O usage information output by the Linux kernel (requires 2.6.20 or later) and displays a table of current I/O usage by processes or threads on the system. At least the CONFIG_TASK_DELAY_ACCT and CONFIG_TASK_IO_ACCOUNTING options need to be enabled in your Linux kernel build configuration, these options depend on CONFIG_TASKSTATS.
iotop displays columns for the I/O bandwidth read and written by each process/thread during the sampling period. It also displays the percentage of time the thread/process spent while swapping in and while waiting on I/O. For each process, its I/O priority (class/level) is shown. In addition, the total I/O bandwidth read and written during the sampling period is displayed at the top of the interface.
Use the left and right arrows to change the sorting, r to reverse the sorting order, o to toggle the –only option, p to toggle the –processes option, a to toggle the –accumulated option, q to quit or i to change the priority of a thread or a process’ thread(s). Any other key will force a refresh.
- Show the version number and exit
- -h, –help
- Show usage information and exit
- -o, –only
- Only show processes or threads actually doing I/O, instead of showing all processes or threads. This can be dynamically toggled by pressing o.
- -b, –batch
- Turn on non-interactive mode. Useful for logging I/O usage over time.
- -n NUM, –iter=NUM
- Set the number of iterations before quitting (never quit by default). This is most useful in non-interactive mode.
- -d SEC, –delay=SEC
- Set the delay between iterations in seconds (1 second by default). Accepts non-integer values such as 1.1 seconds.
- -p PID, –pid=PID
- A list of processes/threads to monitor (all by default).
- -u USER, –user=USER
- A list of users to monitor (all by default)
- -P, –processes
- Only show processes. Normally iotop shows all threads.
- -a, –accumulated
- Show accumulated I/O instead of bandwidth. In this mode, iotop shows the amount of I/O processes have done since iotop started.
- -k, –kilobytes
- Use kilobytes instead of a human friendly unit. This mode is useful when scripting the batch mode of iotop. Instead of choosing the most appropriate unit iotop will display all sizes in kilobytes.
- -t, –time
- Add a timestamp on each line (implies –batch). Each line will be prefixed by the current time.
- -q, –quiet
- suppress some lines of header (implies –batch). This option can be specified up to three times to remove header lines.
- -qcolumn names are only printed on the first iteration,
column names are never printed,
the I/O summary is never printed.
iotop was written by Guillaume Chazarain.
This manual page was started by Paul Wise for the Debian project and is placed in the public domain.