trend calculation for database size

[js1]

On page 37 of the manual:

Housekeeper setting for trends
ZABBIX keeps 1 hour max/min/avg/count statistics for each item in table
trends. The data is used for trending and long period graphs.
ZABBIX database, depending on database type, requires about 128 bytes per
each total.
Suppose we would like to keep trend data for 5 years. 3000 values will require
(3000/1800)*(24*3600*365)*128 = 6.3GB per year, or 31.5GB for 5 years.

Where does the 1800 in the calculation come from? What are its units? Thanks for any clarification.

[nelsonab]

I think it's a typo... Trend data only stores three points per hour.

3000 items * 3 data points/hour * 24 hours/day * 365 days/year * 3 years * 128 bytes

28.2 GB

[js1]

I think it's a typo... Trend data only stores three points per hour.

3000 items * 3 data points/hour * 24 hours/day * 365 days/year * 3 years * 128 bytes

28.2 GB

Would that be 2 data points (min and max) per hour? Thanks for your reply.

[nelsonab]

min/max/average