I read on the forum somewhere (LE: here) that it may not be recommended to use devices over 2 TB with WDTV Play, you may lose the data on them if partitioned incorrectly. Also see other replies here , here and here. If you search the forum I’m sure you’ll find other similar replies.
For reference:
Almost all drives 3TB and larger are shipped formated as “GUID Partition Table” (GPT) instead of MBR (Master Boot Record).
It’s required if you want partitions larger than 2TB.
WD and Seagate both also employ a trick called “Advanced Formatting” which changes the block allocation on the drive and then allows MBR to have larger partitions.
If your TV supports multi-partition drives, you MIGHT be able to re-partition the drive as MBR.
Here’s a pretty good description of both:
