On Fri, 2021-03-26 at 21:46 -0600, Chris Murphy wrote:
On Fri, Mar 26, 2021 at 5:21 PM Patrick O'Callaghan pocallaghan@gmail.com wrote:
I have an external USB-3 2-disk docking station, and a script which can power up and down the drives as needed.
I have a systemd automount unit that correctly powers up the dock when accessed, then mounts the drives (thanks Ed).
After an idle time, automount unmounts the drives. A script detects when this happens and powers them down ... *at which point they immediately power up again, and remain up until I intervene manually, even though they are unmounted*.
This never happens if I run the script directly from the command line (i.e. the drives power down and stay down).
Clearly the docking unit isn't just doing this flakily on its own. Something is making it happen, and I've no idea how to discover what it is except that it seems to be correlated with systemd in some way.
All of the above is 100% reproducible.
I'm open to suggestions if anyone has any ideas.
smartd?
I use this line in smartd.conf to keep it from waking up the drive all the time.
/dev/disk/by-id/wwn-0x5000c500a93cae8a -l selftest -s L/../15/./22 -n standby,250
Since it's unmounted, fatrace won't work, but blktrace will..
blktrace -d /dev/sdb -o - | blkparse -i -
It will generate a lot of lines but it'll also report the process that's sending commands to the drive.
Just to close this off: I looked briefly at blktrace but haven´t had the energy to follow it up (the output need a fair amount of decoding, even with blkparse). I have since switched from MD/ext4 to BTRFS/Raid1, and the dock now powers down the first time and doesn´t come back up again. I´m assuming that MD was the culprit all along for some reason.
poc