How to calculate mysql server reads per second,writes per second?
There are two ways of determining this.

RECENT VERSIONS OF MYSQL

One is to use the performance_schema (assuming 5.6 or higher).

There are many tables that you can query to get at this information, particularly if you have innodb_file_per_table = 1 in your my.cnf.

If you do USE performance_schema there are several tables that can help you to find this information, notably (from DESC TABLES;) 

| file_instances                                     |
| file_summary_by_event_name                         |
| file_summary_by_instance                           |


and 

| table_io_waits_summary_by_index_usage              |
| table_io_waits_summary_by_table                    |
| table_lock_waits_summary_by_table                  |


Then queries such as 

mysql&gt; SELECT SUM(sum_number_of_bytes_read) AS Total_Read 
FROM file_summary_by_instance;

+----------+
|Total_Read|
+----------+
| 10470860 |
+----------+
1 row in set (0.00 sec)
mysql&gt; 


and

mysql&gt; SELECT SUM(sum_number_of_bytes_read) 
+ SUM(SUM_NUMBER_OF_BYTES_WRITE) 
AS Total_IO 
FROM file_summary_by_instance;

+----------+
| Total_IO |
+----------+
| 15161292 |
+----------+
1 row in set (0.00 sec)
mysql&gt;


can help you get the information you want.

OLDER VERSIONS OF MYSQL

If you don't have a recent version of MySQL, then you can use the Unix utility iostat to help you obtain a (reasonably good) estimate of your overall usage.

[pol@localhost inst]$ iostat
Linux 3.11.10-301.fc20.x86_64 (localhost.localdomain)   11/05/15    _x86_64_    (2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           6.33    0.03    2.97    6.12    0.00   84.55

Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
scd0              0.02         0.09         0.00        116          0
sda              13.34       544.46        55.79     742770      76109
dm-0              0.20         0.82         0.00       1116          0
dm-1             16.14       497.16        23.26     678245      31736
dm-2              5.69        42.97        32.52      58628      44364
[pol@localhost inst]$ 


Some of the readings are on a per/second basis, but others represent data from machine bootup. You should obtain a baseline figure (with no MySQL running) and then take your measurements with the RDBMS running and subtract the baseline from the MySQL numbers - that way you will have a reasonable estimate of how much I/O is going on in your server.

iostat is available through the sysstat package which may or may not be installed on your distro - use man iostat (and man sar &amp;c.). The package is available from here. Check out the documentation for your particular system.

For completeness, I should also add that this information is available on an ad-hoc basis through the (excellent) program MySQL Workbench, as shown by the screenshot below: