WDC handles this with a Rocket 620 host bus adapter. You disconnect from sata 0 and use host bus adapter. You will need a sata 0 boot drive less than or equal to 2tb This is for storage not booting. [URL]   Seagate handles this with a driver. [URL] You cannot boot from drives larger than 2TB without GPT partition, 64 bit os, and UEFI Class 2.3.1 bios or higher. [URL] [URL]  
Question:  I use several OptiPlex 990's as internal servers for an intranet + assigned storage with no issues for 5+ years, until recently.... I have a 2TB drive as the main Win7-Pro 64bit OS -and- I use 2 - 4TB drives as the storage, (1 with XAMPP for web services & 1 as assigned storage for users). 1 - 4TB drive crashed, (and I will have to find a way to recover the data) &there is some kind of volume discrepancy in the data remnants of the drive....  I pulled all the drives and replaced them with new ones and came across something I had seen before but ignored  - -  The BIOS displays only 2TB capacity for the 4TB drive(s).....The drives all worked as 4TB in Windows and ran fine. The drives worked as 4TB drives in Windows that is not the question - - 1.  The question is why does the BIOS only display them as 2TB instead of their 4TB size. 2.  If the BIOS only 'sees' 50% of the drive - does that affect the interpretation of of the volume as Windows sees it? 3.  Is there a way to correct that? OptiPlex 990 - A24 BIOS - 16GB RAM - Respectfully,
OptiPlex 990 w/A24 BIOS - 4TB drives display as 2TB in BIOS