Ok so I bought my disks more or less in two batches:
- first batch about 8 months ago (June 2018)
- second batch a month ago (Feb 2019).
All 9 drives show the same make (68LHNPN0), and the same FW (83.H0A83).
First batch was bought from a local dealer in France, while the second batch was bought directly from the WD online store.
I remember having noticed this sound since July 2018, so I guess it must have started right away when I set the disks in my NAS.
I contact WD support back in October about this noise, and had passed 3 drives through DLG, with a “pass” result.
I’ve passed all my disks through the Extended SMART test on the NAS directly, and they all pass.
I do this regularly (I used to run it monthly, now I set it to once per quarter). The test takes ages though (36-48h on the 10TB, used to be around 18h for the 4TB so it looks consistent to me).
I’ve checked the various SMART counters individually, and didn’t notice any suspicious value.
I didn’t notice any performance drop either, nor heating, etc…
And so far, it seems to me only the disks from the first volume make this weird noise.
The first volume is my “main” volume, and all packages are installed on it. I should also add Docker and VMM in the list BTW.
The second volume is only used for storage : backups, long term archives, etc.
I’ve also noticed the noise isn’t produced on a regular basis : I can hear it one day early in the morning, the day after in the middle of the afternoon, etc… as if it was produced every 18 to 36 hours, randomly.
I didn’t manage to narrow it down to a particular activity.
I also noticed that the noise usually appears when disks are not used to write/read anything. Then, if I initiate some activity on the NAS (writing large file for instance), noise vanishes, until the write is finished.
As if something was waiting for low I/O on disks to run, which would trigger the noise.