Add system uptime.
Change rrd data as follows:
5-minute for 3 days
RRA:AVERAGE:0.5:1:864
15-minute for 2 weeks
RRA:AVERAGE:0.5:3:1344
1-hour for 2 months
RRA:AVERAGE:0.5:12:1488
3-hour for 1 year
RRA:AVERAGE:0.5:36:2960