1.    读性能测试命令:

dd iflag=direct if=/home/zhouyan/1.dat of=/dev/null bs=2M count=500


2.    写性能测试命令:

dd oflag=direct if=/dev/zero of=/home/zhouyan/2.dat bs=2M count=500


3.    读写性能测试命令:

dd iflag=direct oflag=direct if=/home/zhouyan/1.dat of=/home/zhouyan/2.dat bs=2M count=500