data safety mechanism

[feiyanzhandui]

We need to keep user data safe! First priority!!!!!!!

Options:

1. Download database manually(or script?) per day/half week?
   pro: keep uptodate data in our hands, no fear for server down
   con: manual operation is painful
   2.All User transactions are written into log file
   pro: record user data automatically
   con: 1. will it become too big for log file? 2. still get risk to lost data when server down 3. data recovery from log will also be painful

Must do:
Keep database safe when deployment