get ec2 volumes from md device

gistfile1.rb

    def get_volumes (mount = nil)
      return [] unless @ec2_instance_id
      mount ||= @datadir
      vols = []
      devs = get_devs(mount)
      instance = @ec2.instances[@ec2_instance_id]
      vols = instance.block_device_mappings.map { |dev,attach| attach.volume.id if devs.include?(dev) }.compact
      return vols
    end

    # connect to the remote host via ssh and get the underlying device names 
    # return array of device names
    def get_devs (mount)
      @ssh || ssh_start
      output = @ssh.exec!("mount").grep(/#{mount}/)
      dev    = output.first.split(/\s+/)[0]

      if dev =~ /^\/dev\/md/
        # it is a RAID device, get the mapping from /proc/mdstat
        output = @ssh.exec!("cat /proc/mdstat | grep #{dev.split(/\//)[2]}")
        return output.scan(/(\D{3}\d+)\[\d+\]\s*/).map{ |x| "/dev/#{x}" }
      else
        return [dev]
      end
    end