Comment # 4 on bug 845319 from Hannes Reinecke

This looks like the companion issue of bug#930487.
'dmraid' has not been updated to use the device-mapper 'cookie' mechanism,
hence it will instruct device-mappper to create device nodes under /dev/mapper
on its own. This means we'll end up with _two_ sets of devices in /dev/mapper,
the udev-created symlinks and the block device nodes create by device-mapper.