Keep in mind, configuring defrag to be less aggressive can result in defrag not keeping up with the write load and eventually hitting stop writes due to lack of available ‘clean’ write blocks. Also making it overly aggressive can negatively affect your peak performance.
The primary parameter to tune defrag is the defrag-lwm-pct. By default this is 50% which causes a 2x write aplification. The write amplification caused by this parameter grows non-linearly.
More information about defrag can be found here: Defragmentation