I am new to graphite/whisper/carbon. I have to create a metric monitoring system where the data is stored in whisper for few days and then is transferred to mysql or any other database.
Is there any way I can define it in the config files or a way to keep polling for data that in whisper and transfer it to mysql manually.
This is almost certainly going to be custom code. You have a couple options. One would be to use Python and write code using the Whisper files to pull the data out and write it to your database. The other would be to use the REST API to pull out the data points and write those to the database.
One thing to consider is the Whisper data format is specifically designed to store this type of data. Depending on what you are doing it is likely you will get better performance by leaving there and figuring out another way to access it, like the REST API.