My Book Mirror Edition drive 'degraded' but which one!?

Hi,
I have a Western Digital 2TB My Book Mirror Edition and one of the drives in a RAID 1 config has become ‘degraded’ according to the WD drive manager software. The LED on the front of the unit is flashing bottom half / top half alternately.

I have ordered another drive  the same…

http://www.amazon.co.uk/exec/obidos/ASIN/B006GDVREI/

I cant seem to be able to work out which of the two drives is faulty though?

Please can you tell me how I work this out?

Many thanks

Gareth

Anyone have any ideas how I work out which drive is ‘degraded’???

It’s ok… I found it!!!

For anyone else looking for an answer to this… go to WD RAID manager then right click on your device and select properties… it tells you the drive status there.

A call to technical support was useless… told me the unit was old and to try and connect it to a pc running an older operating system!!!