Linux - How to perform I/O performance test with dd command

Question : How to perform I/O performance test in Linux to find r/w speed?
Answer :  It can be achieved using dd command.

Example to test write speed :
1. Go to the directory location where you want to perform the test.

[root@server ~]# cd /dir

2. Run dd command below.

[root@server ~]# dd if=/dev/zero of=dd.data bs=4k count=200000 conv=fsync 200000+0 records in 200000+0 records out 819200000 bytes (819 MB) copied, 8.47374 seconds, 96.7 MB/s [root@server ~]# ls -la total 801588 drwxr-xr-x 2 root     root          4096 Oct 22 12:51 . drwxr-x--- 5 root     root           8192 Oct 22 12:51 .. -rw-r--r-- 1 root     root     819200000 Oct 22 12:51 dd.data

Example to test read speed :

[root@server ~]# time time dd if=/path/to/bigfile of=/dev/null bs=8k

                              if = name of input file
                             of = name of output file
                             bs = size of block
                        count = number of block
                         conv = fsync - flush data at the end of the copy
                                   dsync - flush data after every block of the copy