I have done a bit of research on the subject but I am not an expert on SAS, so if someone with more knowledge would like to correct me, please do so.
My guess is that the problem is because the 8TB Seagate drives use 4K sectors and the SAS Controller you are using does not support 4K sectors. If I am correct, I don’t believe that there is anything that you can do about it, other than to get a new SAS Controller that supports 4K sectors.
You can look at the following post to see which SAS Controllers support 4K sectors.
Sorry I don’t have better news for you, but I do hope that it helps.