  This is not the reason. GPT is an OS designation, NOT a physical designation. The PERC 5/6 simply do not support disks larger than 2TB - it is a hardware limitation of tech that is now 10 years old, far older than 3TB drives. 1. A different controller is your only option to utilize >2TB drives, however no other controller is supported on the 2970, so you may find that the controller isn't compatible with the server either. If you decide to try, I would recommend the PERC H700 or an LSI-branded controller. 2. Probably not, but as it is not tested, there may be some strange issues from the controller's side, but I suspect the SIZE will be fine. One thing to watch out for that is a greater danger is the make/model of the 3TB drive ... desktop/laptop and NAS drives do not belong in servers, so if you have a 3TB WD Red, you'll be much more likely to have problems with the model than the size discrepancy.
Hi. I was trying to add some more storage to the Poweredge 2970 I have. But the PERC controller only sees about 2TB of 3TB hardrives. From what I understand, this is to do with the fact that the controller is incompatible with GPT partition tables and is incapable of supporting >2TB HDDs.  I had 2 questions: 1. Is there a solution around this? 2. Is there is any risk of using a 3TB HDD as a 2TB drive. I already bought 2 hard drives.   Thanks.
Poweredge 2970 PERC 5/i installing 3TB hardrives