Vexorg

After a ton of Google-fu I was able to resolve my problem.
 
TL;DR Write cache on drive was disabled
 
found an page called How to Disable or Enable Write Caching in Linux. The artical covers both ata and scsi drives which i needed as SAS drive are scsi and are a total different beast.
 
root@Thor:/etc# sdparm -g WCE /dev/sdd     /dev/sdd: HGST      HUS726040ALS214   MS00 WCE           0  [cha: y, def:  0, sav:  0] This shows that the write cache disabled
 
root@Thor:/etc# sdparm --set=WCE /dev/sdd     /dev/sdd: HGST      HUS726040ALS214   MS00 This enables it and my writes returned to the expected speeds
 
root@Thor:/etc# sdparm -g WCE /dev/sdd     /dev/sdd: HGST      HUS726040ALS214   MS00 WCE           1  [cha: y, def:  0, sav:  0] confirms the write cache has been set
 
Now I'm not total sure why the write cache was disabled under unraid, bug or feature? While doing my googling there was a mention of a kernel bug a few years ago that if system ram was more then 8G it disables the write cache. My current system has a little more then 8G so maybe?