Quick question - if I stop my array, what makes all drives to spin up, will they later normally spin down after 1h of inactivity (in my case), just like when the array is started? Same question about a precleared drive - if I leave it after a preclear, but don't add it to an array, will it eventually spins down?

 

I'm asking because for some reasons I have to stop the array and leave the machine powered on but don't want unnecessarily wear HDDs

Yes for the array drives.  Not sure about pre-clears ... perhaps Joe L will "chime in about that"

 

Quick question - if I stop my array, what makes all drives to spin up, will they later normally spin down after 1h of inactivity (in my case), just like when the array is started? Same question about a precleared drive - if I leave it after a preclear, but don't add it to an array, will it eventually spins down?

 

I'm asking because for some reasons I have to stop the array and leave the machine powered on but don't want unnecessarily wear HDDs

Part of the 'Stop' sequence is to un-mount all the drives.  When a drive is unmounted, a small number of writes to the drive take place.  This is why they spin up when you Stop the array.  Once the array is stopped, the background process that monitors activity to the drives in order to determine if they should be spun down is suspended, hence the drives will not be spun down when array is stopped.  Unassigned drives are never spun down by unRaid OS.  It's possible to program a spindown inactivity timeout in the drive, but unRaid does not use this (because it interferes with spinup-groups feature). This is how it works now.  There would be a use for being able to spin down a particular hard drive, in preparation for removing it.  This is a feature I want to add.

I'm asking because for some reasons I have to stop the array and leave the machine powered on but don't want unnecessarily wear HDDs

 

Clearly I was wrong about the drives spinning down when the array was stopped -- I could have sworn mine have done so, but Tom is clearly the authority on that (I've stopped the array on my v4.7 server for extended times, and thought they had spun down).

 

In any event, you needn't be concerned about "... unnecessarily wear HDDs ..." ==> drives can spin for years non-stop without issue.  In fact, there's some argument about whether it's better to leave them spinning or spin them down.

 

OK, thank you both for clarifying this to me. I also think that 48h shouldn't be such a strain for my disks, especially when they'll probably have their heads parked. I just wanted to be sure and was trying to avoid unnecessary power draw.