Restic pod transfers much larger data than used size of PVC that df command shows

Applies to

Astra Control Service (ACS)

Issue

• When ACS runs backup, Restic which is used as an Astra backup pod sends large data

$ kubectl logs b-cp-kafka-lskgx -n app-1-backup-20211102051418
  : 
{"message_type":"summary","files_new":1391,"files_changed":0,"files_unmodified":0,"dirs_new":349,"dirs_changed":0,"dirs_unmodified":0,"data_blobs":238,"tree_blobs":350,"data_added":231434110,"total_files_processed":1391,"total_bytes_processed":7359614291,"total_duration":4235.635579522,"snapshot_id":"c323f2b3"}

• df command inside the backup target pod shows a much smaller used size for the persistent volume claim (PVC)

$ kubectl exec -it cp-kafka --container cp-kafka-broker sh
sh-4.4# df -h
Filesystem Size Used Avail Use% Mounted on
  :
10.0.2.1:/anf-340b145384b176f0730a4f7dfac9d8af 300G 212M 300G 1% /opt/kafka/data

• ls -lR [PVC mount path] command inside the backup target pod shows the total size of all files in PVC is close to the total bytes that Restic sent