Did you run reclaimation? Archiving works if you delete the files from de
clients and run expiration en reclaimation.
You can see if and how much reclaimation will offer you by doing a select:
select count(*) from volumes where stgpool_name='<POOL_NAME>' and
pct_reclaim>51
(replace <POOL_NAME> with your poolname)
Also check to see if your exchange back-up expire.

Greetings

Karel Bos