I've spent a couple of days trying to pin down what is keeping my disks spinning all the time. I've done all the basic troubleshooting - dockers off, no VMs, etc.

I did pin most of the issue on the Disk Location plugin (see post here).

However after manually updating /etc/cron.d/root without those jobs, I still see something almost immediately wake up my main array disk after I spin it down. I have one main disk and one parity disk, and only the main array disk gets spun back up. Cache probably too, but I don't care about the SSDs.

Using my little chatGPT script to trace back PIDs and PPIDs from lsof, I see the below repeatedly waking the disk at irregular intervals. The trace just brings me back to /usr/libexec/unraid/emhttpd and I don't know enough about the inner workings of Unraid to pull this thread further. I hope somebody may be able to help!

\n--- Disk Activity Detected (Tracing PID 1905290) ---
\nPID: 1905290
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905290 1905286  0 10:48 ?        00:00:00 /usr/sbin/smartctl -A /dev/sdb
\nPID: 1905286
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905286    5058  0 10:48 ?        00:00:00 /usr/bin/php -q /usr/local/sbin/smartctl_type disk1 -A
\nPID: 5058
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root        5058       1  0 Aug20 ?        05:27:39 /usr/libexec/unraid/emhttpd
\n--- Trace Complete ---
\n--- Disk Activity Detected (Tracing PID 1905290) ---
\nPID: 1905290
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905290 1905286  0 10:48 ?        00:00:00 /usr/sbin/smartctl -A /dev/sdb
\nPID: 1905286
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905286    5058  0 10:48 ?        00:00:00 /usr/bin/php -q /usr/local/sbin/smartctl_type disk1 -A
\nPID: 5058
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root        5058       1  0 Aug20 ?        05:27:39 /usr/libexec/unraid/emhttpd
\n--- Trace Complete ---
\n--- Disk Activity Detected (Tracing PID 1905290) ---
\nPID: 1905290
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905290 1905286  0 10:48 ?        00:00:00 /usr/sbin/smartctl -A /dev/sdb
\nPID: 1905286
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905286    5058  0 10:48 ?        00:00:00 /usr/bin/php -q /usr/local/sbin/smartctl_type disk1 -A
\nPID: 5058
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root        5058       1  0 Aug20 ?        05:27:39 /usr/libexec/unraid/emhttpd
\n--- Trace Complete ---
\n--- Disk Activity Detected (Tracing PID 1905290) ---
\nPID: 1905290
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905290 1905286  0 10:48 ?        00:00:00 /usr/sbin/smartctl -A /dev/sdb
\nPID: 1905286
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905286    5058  0 10:48 ?        00:00:00 /usr/bin/php -q /usr/local/sbin/smartctl_type disk1 -A
\nPID: 5058
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root        5058       1  0 Aug20 ?        05:27:39 /usr/libexec/unraid/emhttpd
\n--- Trace Complete ---
\n--- Disk Activity Detected (Tracing PID 1905290) ---
\nPID: 1905290
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905290 1905286  0 10:48 ?        00:00:00 /usr/sbin/smartctl -A /dev/sdb
\nPID: 1905286
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905286    5058  0 10:48 ?        00:00:00 /usr/bin/php -q /usr/local/sbin/smartctl_type disk1 -A
\nPID: 5058
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root        5058       1  0 Aug20 ?        05:27:39 /usr/libexec/unraid/emhttpd
\n--- Trace Complete ---
\n--- Disk Activity Detected (Tracing PID 1905290) ---
\nPID: 1905290
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905290 1905286  0 10:48 ?        00:00:00 /usr/sbin/smartctl -A /dev/sdb
\nPID: 1905286
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905286    5058  0 10:48 ?        00:00:00 /usr/bin/php -q /usr/local/sbin/smartctl_type disk1 -A
\nPID: 5058
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root        5058       1  0 Aug20 ?        05:27:39 /usr/libexec/unraid/emhttpd
\n--- Trace Complete ---
\n--- Disk Activity Detected (Tracing PID 1905290) ---
\nPID: 1905290
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905290 1905286  0 10:48 ?        00:00:00 /usr/sbin/smartctl -A /dev/sdb
\nPID: 1905286
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root     1905286    5058  0 10:48 ?        00:00:00 /usr/bin/php -q /usr/local/sbin/smartctl_type disk1 -A
\nPID: 5058
=============================
UID          PID    PPID  C STIME TTY          TIME CMD
root        5058       1  0 Aug20 ?        05:27:39 /usr/libexec/unraid/emhttpd
\n--- Trace Complete ---

Have you got any plugins running?

If a file(s) is in use on the disk in question, it will not spin down. Usually this is due to appdata being spread out onto the array, but diagnostics might help figure it out

Thanks for the replies guys, I don't think a file is in use, because the disks do initially all spin down and then the one in question will spin back up in the next 1-15 minutes usually from what I've seen.

I do have some plugins, but the only one disk related I believe is Disk Location which I discussed seeming to find a (temporary) fix for. I can try looking at the diagnostics, maybe that will help. I'm not very familiar with them.