If you want to stress-test your TSM server to check how fast a backup is without accessing the tapepool you can easily generate diskpools. Though, if you have no space for your backup there is a hidden option for dsmserv.dsk that writes all data of diskpools to /dev/null.
If you have set this, and create filediskpool volumes, the volumes will be filled up with data, which will be piped to /dev/null.
Really a nice addon to check the real speed of a backup.
Be careful if you leave this option on your TSM Server and create filediskpools you want to use. Your data will be lost during migration to the filediskpool. So delete this option out of your dsmserver.dsk file if you do not need it any longer.