关于lat(I/O completion latency)、clat(complete latency)、slat(summit latency)：

lat is the total latency. slat is the time it takes to submit the
IO to the kernel, clat is the time from when slat is over and until the
device has completed it (and the application is notified). Hence lat is
slat + clat.

1、rw_sequencer

identical或者sequential

如rw=randread:8 这样每8次io就更改一次offset。那么这个rw_sequencer控制在这8次的io时的offset。

2、#!/usr/local/bin/fio  --debug=io

使用debug选项可以看到它的io的详细情况

3、rw=randread:51200

表示每51200次io重新取offset

4、file_service_type=random:51200

表示每51200次io重新随机取下一个文件