pg_upgrade --link

Hi Team,

I have performed the production database upgrade from postgresql 13 to 17
version using pg_upgrade --link method on ubuntu 22.04 successfully.

Now after few days of upgrade, while dropped one database of size 900+ GB
successfully, the space not get reclaimed physically from mount point
/usr/pgdata.

Old PG13 data directory: /usr/pgdata/data1 --> size 4.5TB

New PG17 data directory:
/usr/pgdata/data17 --> 5.6GB

I didn't perform the delete_old_cluster.sh yet.

I can see that the oid of this dropped database is present in PG13 data
directory base location and occupying 972GB size, while it's not present in
PG17 data directory base location.

Now my doubt is if I removed Old data directory, will it cause any impact
on running PG17 cluster.

Please suggest the best and safe approach to reclaim the space.

Thank you so much..

Regards,
BPratap