Recently I noticed that I have insufficient disk space.
I checked disk usage and noticed that my Postgres database consumes 375GB, however my Persistent Volume storage is setup only on 5GB.

I have checked the PV and PVC:

Name:          postgres-volume-claim
Namespace:     default
StorageClass:  local-storage
Status:        Bound
Volume:        postgres-volume
Labels:        app=postgres
Annotations:   pv.kubernetes.io/bind-completed: yes
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      5Gi
Access Modes:  RWX
VolumeMode:    Filesystem
Used By:       postgres-8475b9554f-czjq8
Events:        <none>

Name:            postgres-volume
Labels:          app=postgres
Annotations:     pv.kubernetes.io/bound-by-controller: yes
Finalizers:      [kubernetes.io/pv-protection]
StorageClass:    local-storage
Status:          Bound
Claim:           default/postgres-volume-claim
Reclaim Policy:  Retain
Access Modes:    RWX
VolumeMode:      Filesystem
Capacity:        5Gi
Node Affinity:   <none>
Message:         
Source:
    Type:          HostPath (bare host directory volume)
    Path:          /mnt/raid/db
    HostPathType:  
Events:            <none>

And the disk usage of mounted directory:

4,0K    db/pgdata/pg_twophase
4,0K    db/pgdata/pg_stat
832K    db/pgdata/pg_subtrans
4,0K    db/pgdata/pg_wal/archive_status
7,5G    db/pgdata/pg_wal
4,0K    db/pgdata/pg_snapshots
592K    db/pgdata/global
4,0K    db/pgdata/pg_serial
4,0K    db/pgdata/pg_replslot
4,0K    db/pgdata/pg_tblspc
12K db/pgdata/pg_multixact/members
12K db/pgdata/pg_multixact/offsets
28K db/pgdata/pg_multixact
12K db/pgdata/pg_notify
161G    db/pgdata/base/16476
7,6G    db/pgdata/base/pgsql_tmp
199G    db/pgdata/base/16477
7,4M    db/pgdata/base/1
7,9M    db/pgdata/base/452050895
7,6M    db/pgdata/base/13067
7,4M    db/pgdata/base/13066
8,6M    db/pgdata/base/30664
367G    db/pgdata/base
5,6M    db/pgdata/pg_xact
4,0K    db/pgdata/pg_dynshmem
4,0K    db/pgdata/pg_logical/snapshots
4,0K    db/pgdata/pg_logical/mappings
16K db/pgdata/pg_logical
116K    db/pgdata/pg_stat_tmp
4,0K    db/pgdata/pg_commit_ts
374G    db/pgdata
374G    db

How is it possible that mounted directory of Persistent Volume is much bigger than 5Gi?