Thanks to all for your very helpful replies !
As Greg Smith rightly said, i faced a problem of missing connections between the runs. I even ran the cron every less than a second, but, still that would become too many runs per second and later i need to take the burden of calculating every thing from the log.
I did not really calculate the IO load while the logging is on. I would switch on "log_connections" and "log_disconnections" to log the number of connections and duration of a connection.
If i notice high IO's and huge log generation, then i think Greg Spileburg has suggested a good idea of using tcpdump on a different server. I would use this utility and see how it works (never used it before). Greg Spileburg, please help me with any sources of documents you have to use "tcpdump".
Thanks again and sorry for replying late on this !
Regards,
Venkat