Portablity of Tomcat

im working on jsp,and im using tomcat running in win2000 , later i want to port it to linux, i didn’t know much about porting, so any body please help me out in this regard,
and also im using files for teporary storage,later i want to use MySql for storage,
and help me in how i can use the files efficiently to store data and retrive,

here i need to store data, retrive and compare with new entry like these stuff i need to do,

so please help me,

thanks in advance,
charan