I have four hard drives on my NAS.
Three (Western Digital, all of the same model) are put into standby mode (turn down) by
hd-idle and they stay on hold until you use them. The reason why I use
hd-idle and not the internal mechanism of energy saving through
hdparm (-S XX /dev/smth) is that these units do not support it.
Here comes the problem:
The fourth (Toshiba) can be rejected by
hd-idle and also manually by
hdparm (-y /dev/drive4) but he wakes up after about 30 minutes (sometimes earlier, sometimes later) … every time.
I tried several things:
Turn off hd-idle all together. (Maybe it causes awakenings in some way). It didn't work.
Try different settings to
hdparm -S XX /dev/drive4 (internal waiting time) and
hdparm -B XX /dev/drive4 (internal power management settings). No, he still wakes up after a while.
iostat if the unit was used by something. Without use what never.
Everything is disassembled.
Also, the drive is part of a group of LVM and FS volumes with the other drives in the system and I'm pretty sure that if some process would trigger the drive, it would wake up all the other drives as well.
I have no idea what's going on here.
Has anyone experienced this?
How can I improve my debugging?
On a side note: I know that turning hard drives up and down constantly is bad, but sometimes I don't need the drives for long periods of time and prefer to have them standby during this time.