How to keep one record for data transfered by ftp?

Hello everyone,

I'm using Red Hat AS3 and set up ftp server with vsftpd. I need to keep one
backup for those data transfered by, that is to say, if you wanna upload
data to the site, either download from it, the server will keep one backup
and record log information automatically even you don't know the process.
but I have no any idea. I also don't know the mechanism of ftp data
transfer, Who may give me some advice kindly? Thanks for your help!

Have a good day!

B.R.

Joffre