I got an issue with a new CACTI machine. Everything seems to be working ok:
1. The poller runs every 5 minutes, I see in the cacti.log that indeed values are being retrieved from the specific OIDs and the rrdtool update command is being used to store the information in the data sources.
2. The permissions of rra folder was checked, I even changed it to 777 just to be sure everything is ok
3. I've created manually a test rrd file and tried to manually update it and indeed it doesn't work, when I do the fetch command there are no values stored beside the ones of NAN. I've tried to do the same on a working CACTI machine and I can successfully visualize the values that I have manually stored.