A couple more FCM performance tips for you. We have released the fix for APAR IC86558 for the TSM Server. It is included in 6.2.5 and 6.3.4. This change allows the TSM Server to manage lots of small files more efficiently in certain situations. For those using Exchange 2010 (which has thousands of 1MB transaction logs), I highly recommend getting this fix. For those running Exchange 2007 and backing up using VSS, I would also recommend this fix. This fix may also help those using FCM to backup their file systems and custom applications, depending on the type of files being backed up.
Secondly, I would like to discuss the BUFFers and BUFFERSIze parameters. For legacy backups, the Data Protection process performs the backups, so these parameters are used. However, for VSS backups, the DSM Agent performs the majority of the transfer to the TSM Server, so you will want to tune the baclient parameters instead. (Be sure to restart the DSM Agent for the changes to take effect). In both cases, though, the default values are the optimal values for most environments.