Yes I think that may be part of the issue, however as far as I can tell whoever installed CentOS 6 on here set it up with 1 array using all 8 x 1 TB drives, so based on what I see in the bios therre is one 7TB drive (raid 5). The reason being I suppose that the OS file systems use only around 150GB and the rest is used as a /data volume (about 6.5 TB)
So the question is if that setup works with CentOS 6, there must be something different with CentOS 7 that doesn't allow that same raid setup without changing the way the drives are defined. If one drive is used for the OS than we will not have as much space left to match what's already there for /data
thx