We run a cluster of openvz servers and are looking for a way to automatically graph the content of user_beancounters for all ves. We currently have a fairly rudimentary cron which alerts us when limits are hit but we could like a graphing solution to show us history.
Obviously we could roll our own using some fancy bash/php/perl and rrdtool but we're wondering if there are any existing solutions before we go down this path.
We current run a cacti/snmp based graphing infrastructure.
If you aren't already aware of it, the Better cacti Templates project has some OpenVZ graph templates that may be helpful to you. I couldn't see anything regarding user_beancounters on the OpenVZ page but their data collection script would be a good framework to extend yourself to collect whatever you want.