I configured my system to spin down the HDD pool after 1h (as I rarely need it). I set the encryption type to ‘key’ and, at the same time every day, my HDD pool was woken up. In the monitoring, I found a short write access with 20kb/s. I have no idea what TrueNAS is doing here.
The time of the HDD-access seemed to change after a reboot. ~02:06, ~08.00, ~19.10.
Solution: After reading the mentioned thread, i changed the encryption type to ‘passphrase’ and now my HDDs keep sleeping
I’m skeptical.
I don’t follow how key encryption would be the cause of your pool spinning up.
Once the key encrypted pool is unlocked at boot, it doesn’t need to read the key anymore.
If it was truly related to the config backup done every day, it would always happen at 03:45 in the morning, assuming your clock is set up properly on the server.
I think the culprit is something else. The location of the system dataset and SMART are the typical go-to suspects, but I imagine apps probably trigger spinups as well.
I was also skeptical and i doesn’t make sense to me
You’re right, backup happens at 03:45. That was my first thought too.
But the config backup happens every day at 03:45 reliable, timestamps are ok. So it’s not the backup.
I’ve configured SMART for only do checks when HDDs not in standby. I also turned SMART service on and off. No effect.
Apps are not installed. Only SMB, but the only PC that is connecting to, was offline at these times.
test case:
encryption ‘key’: spin up
encrpytion ‘passphrase’: no spin up
encryption ‘key’: spin up
encrpytion ‘passphrase’: no spin up
– and no other configuration changes between them.
As I said, I don’t know exactly what the reason was, but it worked for me and maybe it will help someone else. But I would still be very interested to know the background to this.
