Size of PostgreSQL backup ./. Sybase DUMP

Hello,

We migrated a customer from Sybase ASE 15.7 to PostgreSQL 11.10, both on
Linux server. With Sybase you create DUMP of only the database in
question, not the server, and the gzip'ed DUMP files is around 2,6 GByte in size.

For PostgreSQL we do backup with something like this cmd:

pg_basebackup -U ${DBSUSER} -Ft -z -D ${BACKUPDIR}-${DATE}-${NUM}

The resulting files

# ls -lh backup-20210416-3
insgesamt 999M
-rw------- 1 postgres postgres 999M 16. Apr 14:02 base.tar.gz
-rw------- 1 postgres postgres 17K 16. Apr 14:02 pg_wal.tar.gz

are less than 1 GByte.

Any ideas about the cause of the difference? Can the backup somehow be
checked without doing a recovery-restore in a new server?

Thanks

matthias
--
Matthias Apitz, ✉ guru(at)unixarea(dot)de, http://www.unixarea.de/ +49-176-38902045
Public GnuPG key: http://www.unixarea.de/key.pub
¡Con Cuba no te metas! «» Don't mess with Cuba! «» Leg Dich nicht mit Kuba an!
http://www.cubadebate.cu/noticias/2020/12/25/en-video-con-cuba-no-te-metas/