Re: Size of PostgreSQL backup ./. Sybase DUMP

On Fri, 2021-04-16 at 15:47 +0200, Matthias Apitz wrote:
> 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?

I don't know anything about Sybase, but if that dump is something
akin to "pg_dump", then you are comparing apples and oranges.

Moreover, the base backup is compressed, and I don't know if the
Sybase dump is.

If you had used PostgreSQL v13, you could check the backup for
completenes. But the best test for a backup is to restore it.

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com