im currently running Windows Server 2012 R2 with a HGST (Hitachi) z7k500-500 2.5 SATA drive.
I have a Smart Array E200i.
Read is about 140MB/S but write is only from 7-14MB/S.
I already updated the smart array firmware but same problem.
I checked the disk for bad sectors but everything ok.
The disk was completly new and is only 2 days old.
I dont have any comparsion (like crystaldiskmark) to 10k SAS drives but i remember that they're very very faster.
screenshot: http://prntscr.com/ex93ic