Python reliable project setup: write data from a serial port to a database in a certain time interval
For detecting system shutdown compare time stamps of last reading taken to current reading's time stamp. If they differ by more than 15 minutes than something went wrong during the operation.
The application should read data from a serial port every 15 minutes (using the Modbus Protocol) and put them into a database. The data can then be viewed and manipulated in a web interface. I'm using Windows (no server) with a RAID system to prevent data loss.
My current setup looks like this:

using pyserial and minimalmodbus for reading the data and putting them into a MySQL database
setting a cron job to run the script every 15 minutes (alternatives?)
using Django in order to have a neat interface where one can view stats and download the data as a *.csv file

My questions are:

Does this setup makes sense concerning reliability; do you have any improvements?
How can i detect if the system has experienced a shutdown and i lost some data?