Mac OS 10.10.5
Early 2009 Power Mac
G/Drive Enclosure #F30S2JAD GD4 2000 (Originally 2TB)
The 2TB drive failed in my out of warranty enclosure, so I installed a WD Enterprise 4TB.
Hooked up via FW800, or USB 2.0, the drive showed as 1.8TB in Disk Utility when I tried to initialize/format it.
I used a raw drive USB hookup and it showed as 4TB and I was able to initialize/format it, no problem.
Back into the G/Drive enclosure and the drive was formatted & named, but still showed as 1.8 TB.
I tried a Mercury enclosure via FW800 and it also showed 1.8TB.
When I ran disk utility repair, it showed “partition map check failed because no slices were found”.
This was the same when in the G/Drive & Mercury enclosures.