Use dd command to monitor the reading and writing performance of a disk
device:

1. Open a shell prompt.
2. Or login to a remote server via ssh.

3. Use the dd command to measure server throughput (write speed)
   dd if=/dev/zero of=/tmp/test1.img bs=1G count=1 oflag=dsync

4. Use the dd command to measure server latency
   dd if=/dev/zero of=/tmp/test2.img bs=512 count=1000 oflag=dsync

ref：
https://www.cyberciti.biz/faq/howto-linux-unix-test-disk-performance-with-
dd-command/