В статье, которую правильно дал Брайан, указан следующий код:
require 'win32ole'
file_system = WIN32OLE.new("Scripting.FileSystemObject")
drives = file_system.Drives
drives.each do |drive|
puts "Available space: #{drive.AvailableSpace}"
puts "Drive letter: #{drive.DriveLetter}"
puts "Drive type: #{drive.DriveType}"
puts "File system: #{drive.FileSystem}"
puts "Is ready: #{drive.IsReady}"
puts "Path: #{drive.Path}"
puts "Root folder: #{drive.RootFolder}"
puts "Serial number: #{drive.SerialNumber}"
puts "Share name: #{drive.ShareName}"
puts "Total size: #{drive.TotalSize}"
puts "Volume name: #{drive.VolumeName}"
end