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I am using BitTorrent Sync on my Raspberry Pi (Raspbian) which syncs files on the external hard drive (ext4). I wrote a small script that spins down the drive after 5 minutes of inactivity. As soon as I read something it starts to spin again, so that seems to work fine.

Here is the spindown script which is executed every 5 minutes via cronjob:

# !/bin/sh

# Get new state from diskstats
NEWstate=$(cat /proc/diskstats | grep $1)
echo $NEWstate > /home/pi/bin/spindown/NEWstate.txt

# compare md5 sums
md5new=$(md5sum /home/pi/bin/spindown/NEWstate.txt | sed 's/ .*//')
md5old=$(md5sum /home/pi/bin/spindown/OLDstate.txt | sed 's/ .*//')

# if no changes, power down
if [ "$md5new" = "$md5old" ]; then
        sdparm --flexible --command=stop /dev/$1 &>/dev/null
fi

# Write current state to file
echo $NEWstate > /home/pi/bin/spindown/OLDstate.txt

But after a few hours the hard drive is being unmounted and BT Sync can not work properly anymore. I want to use it as a private backup server so it should run all the time.

It's mounted via the /etc/fstab file like this:

/dev/sda5 /media/External ext4 defaults,noatime 0 0

Is there a way that remounts the drive automatically as soon as it gets unmounted or (even better) prevents it from doing so?

  • How are you mounting the external drive? – jasonwryan Nov 5 '13 at 21:07
  • Via /etc/fstab with default settings – Nixatty Nov 5 '13 at 21:12
  • Maybe it depends on the spindown script which uses sdparm after the hard drive has been inactive for 5 minutes. But does Raspbian unmount a spinned down drive? – Nixatty Nov 5 '13 at 22:13
  • 1
    /etc/fstab looks good. Please post the script you are using. – jasonwryan Nov 5 '13 at 22:15
  • I updated the question. The script works fine and the drive is spinned down after 5 minutes of inactivity. – Nixatty Nov 5 '13 at 22:29
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I would try changing the power management setting on the HDD via hdparm.

$ hdparm -B <value> /dev/sdx

Details

-B     Query/set Advanced Power Management feature, if the drive supports it. 
       Allow value means aggressive power  management  and  a high value means 
       better performance.  Possible settings range from values 1 through 127 
       (which permit spin-down), and values 128 through 254 (which do not permit
       spin-down).  The highest degree of power management is attained  with a 
       setting of 1, and the highest I/O performance with a setting of 254.  A 
       value of 255 tells hdparm to disable Advanced Power Management altogether 
       on the drive (not all drives support disabling it, but most do).
| improve this answer | |
  • Thank you, but the drive doesn't seem to support hdparm. – Nixatty Nov 6 '13 at 18:18

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