I have Yosemite 10.10.2 on my Early 2008 24". Time Machine has been backing up to my WD external hard drives for years. I just purchased a new 2TB My Passport using USB 3.0. It's formatted in Mac OS Extended (Journaled). The device shows up on by desktop and it does store files that I drag into it. However, Time Machine does not recognize it.
Any thoughts? Is it Time Machine or the 3.0 USB?
Best Answer
This article is quite old, but I think is probably the reason…
Source: Macworld - Time Machine tips and troubleshooting
Apple's KB doesn't seem to quite be so explicit - OS X Yosemite: Disks you can use with Time Machine
You would need to go to Disk Utility & check the drive is formatted as not only Mac OS X Extended, but that the underlying structure is GUID [most 3rd party drives will arrive as MBR/NTFS usually for Windows]
You can only change from MBR to GUID by completely erasing the drive & starting over…
Select the drive itself [not the volume]. Bottom right it will tell you the partitions scheme.
If it is not GUID, then > Partition. Select a Partition layout [not current], then Options… & set to GUID Partition Table.