MD3220 - low speed from cache

Hello,

I have MD3220 and VM on ESXi 6.0

VM app need access with 64KB block and QD=1

I tried to test to evaluate the maximum read performance of the controller from cache with this access specs:

Iometer 1.1.0

Maximum Disk Size = 1024 Sectors
#of Outstanding I/Os = 1 per target
Access Specifications:
64 Kib; 100% Read; 0% random

and get only ~3300 IOPS!

why speed from cache so slow?

cache is like ram-disk, and speed should be very high.