Ubuntu HDD idle time

sudo hdparm -S 200 /dev/sda

/dev/sda:
 setting standby to 200 (16 minutes + 40 seconds)

#hdd status 

hdparm -C /dev/sda

#config file

cat /etc/hdparm.conf 

hdparm -B 1 -Y /dev/device
hdparm -B 255 /dev/device

The first hdparm put the device standby immediately. The second one turn off APM, so the disk stay in standby mode till the next disk access.

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Notes for repairing degraded RAID 1

cat /etc/fstab
cat /proc/mdstat
sudo mdadm --query --detail /dev/md127
sudo mdadm /dev/md127 --remove /dev/sda2
sudo mdadm --add /dev/md127 /dev/sda2
watch -n3 cat /proc/mdstat

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