There are a number of different processes that run in the exempt domain so it isn't really possible to unpick from these graphics.
I did, however, have a look at an AutoSupport for that system and it looks like one of the volumes has storage efficiency scheduled to run at 1500 on a daily basis. This lines up nicely with the spike in the chart.
If you don't see this spike every day then it may simply be because someone dumped a whole load of data into that volume and created a lot of work for the deduplication and compression engines.
Regards,
Warren