I/O Calibration returns maximum latency 0

 I have two 11.2.0.3 databases running on different storage systems. When I run I/O calibration I give both the parameters 12 drives 25ms maximum latency. The one always returns 25ms latency while the other always returns 0.  The MB/s and IOPS values are about what I would expect. What does that 0 return value mean?  The main difference in the storage is the one that returns 0 does not have an NVRAM write cache while the other does.