I have tried fiddling around with just about every option available when setting up iscsi lun on freenas and i still cannot get my system to play nicely with storage spaces on windows 2012 R2. I know it's not with the instance of the windows server , as i get the same error on other 2012 R2 servers also. What i have found , is that frenas 9.2 works with 2012 R2, so i hope someone else has seen this issue using the freenas build i am using and can help me get past this hump. One last thing, I found out by trial and error , is that if i use a non freenas iscsi lun to create the initial storage space pool, then add the freenas lun , it can be added with no problem and works as expected. The problem is only seen when i try to use the freenas lun to create the pool. Also if i use windows disk manager i can use the iscsi lun with no problem.