After some time of using my new TrueNAS, I noticed that the hard drives for the main pool never wanted to spin down. I tried various configurations, but they never seemed to have time to relax. As I was checking out the I/O, it became clear to me that every second or so, a few kilobytes was being written to all the disks of the zpool... And since I had some Apps running in the same pool as my actual archival. Then I presumed that it was simple Application/Docker/Kubernetes logs being written here and there as they are doing basic checks.
I was lucky enough to have an 256GB NVME laying around, which I then installed into the cluster.
I setup a stripe pool with a single new drive added. TrueNAS really wanted to warn me about replication, but this is purely for Application data like the binaries and logging. No content, media or actual data.
I went into Apps, settings, choose pool and selected the new NVME pool. I felt slightly insecure in what this setting would actually do; would it also move mounts as well? or anything else? I just kind of jumped into it and it seemed to just migrate the apps to another pool. Excellent!
And... It work! The disks in the HDD pool are not barely doing anything, I am seeing tiny bit of writes on the new pool (~200KiB/s).
Picture above shows during migration. Top graph is one of the HDDs from the pool. Bottom graph is NVME.
Picture above shows usage few hours of migration. Notice no activity on the HDD.
Before the change, the power usage was around 37W and now it is around 24W (after a few minutes of not doing anything). I am still a little unsure if they actually spin down. The noise is lower, less low-frequency vibration, and whenever I start accessing anything it definitely sounds like something starts kicking up!
So, with lower noise and less watt usage, then I'm pretty happy :-)