Quick-and-dirty script to find out the spin-down time of my external HDD

find_spindown.rb

#!/usr/bin/env ruby

require 'benchmark'

# Access HDD (on /dev/sdb?)
# If it takes too long to respond, it has spun down
CMD = 'ls /data/Videos >/dev/null'
# Range of minutes to wait. Spin-down should be within this range
WAIT_MINS = [44, 45]
# If it takes longer than this (secnods), disk has spun down
THRESH = 3

WAIT_MINS.each do |m|
  puts "waiting for #{m} mins"
  sleep 60 * m

  dur = Benchmark.realtime { system(CMD) }

  print '=> '
  if dur > THRESH
    puts "spin-down is #{m} mins!"
    break
  else
    puts "Passed #{m} mins but not yet"
  end
end