The examples in the lustre manual that show how to enable jobstats often use the "lctl conf_param" command. This will cause all clients to use the same env variable for reporting jobstats. However, it can be useful to customize this based on the client's functionality. For example, you can use "lctl set_param jobid_var=PBS_JOBID" on compute nodes so that they report stats on a per-job basis. Then you can use "lctl set_param jobid_var=procname_uid" on login nodes to reports stats based on process name and UID. Then if your MDT gets slammed, you should be able to easily tell if the traffic is coming from a batch job or a user running an interactive command. And if it is an interactive command, you will have the process name and the user's UID. (I was able to use this to track down a Lustre client that was slamming our MDT because it was misconfigured and trying to index our Lustre file system for the "locate" command database.)