Spindown every /sys/block/sd* device after specified idle time.
This is useful because typically hdparm doesn't spin down external
drives.

This was developed and tested in Ubuntu Jaunty, but should work in
subsequent releases. The script needs the package sdparm and root
privileges. The most common use is to launch it within rc.local at
boot time.

For example, in a home server that is mostly idle, internal hardrives
can be set to spindown through hdparm, and external drives through
this script by adding the following lines to /etc/rc.local before the
`exit 0` statement.

rc.local
--------
#Spindown internal HDD after 10 minutes
hdparm -q -S 120 /dev/sda

#And also every external drive after 10 minutes
/etc/init.d/scsi-idle 600 &


Usage
-----
Syntax:
    spindown [-h] | [[-i seconds] | [-s] | [-e sda [-e sdb ...]]]

Parameters:
    -h, --help      this help screen
    -e, --exclude   do not operate on specified drive
    -i, --interval  idle seconds above which the drives should spin down
    -s, --simulate  do not perform actions, just simulate what would happen