Here is a search that I often use to check on how much data is being sent per hour, by forwarder.
index=_internal source=*metrics.log group=tcpin_connections
| eval sourceHost=if(isnull(hostname), sourceHost,hostname)
| rename connectionType as connectType
| eval connectType=case(fwdType=="uf","univ fwder", fwdType=="lwf", "lightwt fwder",fwdType=="full", "heavy fwder", connectType=="cooked" or connectType=="cookedSSL","Splunk fwder", connectType=="raw" or connectType=="rawSSL","legacy fwder")
| eval version=if(isnull(version),"pre 4.2",version)
| rename version as Ver
| fields connectType sourceIp sourceHost destPort kb tcp_eps tcp_Kprocessed tcp_KBps splunk_server Ver
| eval Indexer= splunk_server
| eval Hour=relative_time(_time,"@h")
| stats avg(tcp_KBps) sum(tcp_eps) sum(tcp_Kprocessed) sum(kb) by Hour connectType sourceIp sourceHost destPort Indexer Ver
| fieldformat Hour=strftime(Hour,"%x %H")
Just copy this search and paste into your search box - and pick a relatively short time period (like last 24 hours or less). It should run on any Splunk 4.2 or newer. It might work on older versions, but I am not sure...
You could change the stats command if you wanted a slightly different output. For example, replace the last 3 lines with the following to get an overall summary by forwarder, rather than hour by hour statistics:
| stats avg(tcp_KBps) sum(tcp_eps) sum(tcp_Kprocessed) sum(kb) by connectType sourceIp sourceHost destPort Indexer Ver