A Three-way Mirror adds additional IOPS per stored block and higher level protection against failures
calibrate_io.sql – attempts to measure random I/O performance with two numbers: maximum number of IOPS and average latency at which it is measured
ORADATA with Three-way Mirror
Max IOPS=212717
Max MBps=1371
Latency =1
ORADATA with Two-way Mirror
Max IOPS=178370
Max MBps=1278
Latency =1