Все у вас нормально. Привожу мой тест двух SSD в RAID:

Sequential Read (Q= 32,T= 1) : 758.637 MB/s
Sequential Write (Q= 32,T= 1) : 721.695 MB/s
Random Read 4KiB (Q= 32,T= 1) : 322.459 MB/s [ 78725.3 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 360.153 MB/s [ 87928.0 IOPS]
Sequential Read (T= 1) : 618.020 MB/s
Sequential Write (T= 1) : 583.806 MB/s
Random Read 4KiB (Q= 1,T= 1) : 28.761 MB/s [ 7021.7 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 68.758 MB/s [ 16786.6 IOPS]

Test : 1024 MiB [C: 22.7% (108.2/476.2 GiB)] (x5) [Interval=5 sec]
Date : 2016/01/13 11:35:47
OS : Windows 10 Professional [10.0 Build 10586] (x64)