You can add the fields supported by the collectd package. Info supplied with collectd is used by RRDTools backened, which is used for Reporting. Unfortunately, the collectd supplied by FreeNAS is the standard package not suitable for the role. FreeNAS says NUT and UPS is supported, but the collectd is compiled with "NUT=no", which is very bad. Also, IPMI support is completely missing. Wish these bugs would be fixed soon.