If you are running on Windows, you might also want to look into using nsrperf. It's a little known binary that ships with NetWorker. It allows you to turn on some useful perforamnce objects that windows performance monitor can take advantage of. Simply type nsrperf -y from command line, and the following objects will become available in Windows Performance monitor...
Perfmon Objects Instance Counter NetWorker Attributes
NetWorker Device <device name> Rate “last rate” in Device statistic attribute
NetWorker Device <device name> Sessions “sessions” in Device statistic Attribute
NetWorker Device <device name> Errors “errors” in Device statistic Attribute
NetWorker Session <session id> Rate “rate kb” in the Server sessions attribute
NetWorker Session <session id> Amount “amount” in the server sessions attribute
Of course, using performance monitor will allow you to log, graph, etc.