I am collecting SNMP data on-site for a number of systems, currently using Cacti. These systems are spread on a number of sites that aren't always connected to internet, but I also need to centralize the data on a single system (datacenter housed server) and get graphs out of it.

If I directly poll remote systems with a centralized Cacti I'd loose data when a site is not connected to internet. I should record data on-site (I have a server at each site and I can run whatever I want on it) and then 'sync' everything to the central system.

One hack could be a cacti or directly an rrdtool on site and then periodically rsync RRD data to the central Cacti system, but that doesn't sound like a 'clean' solution: every RRD would have to be defined at both places and rsync scripts setup with the specific file names.

Can you suggest a better solution? Cacti is not a requirement but I'd like to use something like that on the central system. On-site systems need only to collect data I don't need to graph it there or manage users rights to view data and stuff like that, users will only access the centralized system.