I have four HDDs in my NAS.
Three (Western Digital, all the same model) are put in standby mode (spin down) by
hd-idle and they stay in standby until I use them. The reason I use
hd-idle and not the internal power saving mechanism via
hdparm (-S XX /dev/smth) is that those drives do not support it.
Here comes the problem:
The forth (Toshiba) can be spun down by
hd-idle and also manually by
hdparm (-y /dev/drive4) but wakes up after around 30 minutes (sometimes sooner, sometimes later)...every time.
I tried various things:
Shut down hd-idle all together. (Maybe it causes the wake-ups somehow). Did not work.
Try different settings for
hdparm -S XX /dev/drive4 (internal standby time) and
hdparm -B XX /dev/drive4 (internal power management settings). Nope, still wakes up after a while.
iostat if the drive was used by somethings. No usage what so ever.
Everything is unmounted.
Also the drive is part of an LVM volume group and FS with the other drives in the system and I am fairly positive that if some process would wake up the drive, it would also wake up all the other drives.
I have no clue what's going on here. Has anyone experienced this? How can I enhance my debugging?
On a side note: I know that spinning HDDs up and down constantly is bad, but I sometimes do not need the drives for long periods of time and would rather have them be in standby for this duration.