How much storage does the S9 deice use on the SD card?

A 1GB SD card will easily store 5 years of S9 data. The S9 is constantly re-writing data, so at any point you should only see 365 days of summary data, 30 days of detailed data and 7 days of high resolution data. This data takes up a fraction of the space on the SD card itself, and the card will never “fill up”.