Some questions about encrypted Jail backups (cloud sync)

[brennoflavio]

I'm trying to understand why some backups have larger size in the cloud and why some of them fails to backup while other works just fine.

I have a jail that runs a PostgreSQL database with a dataset

Code:

 /mnt/default/postgres/data 

mounted in the data folder

Code:

/var/db/postgres

so I can keep database data outside the jail for snapshot / backup purposes.

This dataset currently has 66mb reported by TrueNas UI, and after setting up a encrypted cloud sync task using a Backblaze bucket, it ran successfully, with a reported size of 127.1mb so 1.92x the original size.

This does not happen with other backups I have. For example, I have a similar setup for my Nextcloud data folder which has a reported size of 203.6GB by TrueNas and 222.5GB by Backblaze, far closer.

I also have another PostgreSQL database for an application setup in the same way that described before, with a 4GB size, that always fails with some timeout response from the host (after uploading ~10gb of data).

So I was asking myself why those difference in size happens and why my larger database fails to backup. Maybe it is because of the size / type of files that PostgreSQL generated and encryption increases it size, and for the larger db it becomes too big to upload it properly. But I don't know.

I know I could use PostgreSQL tools like pg_dump to backup the db, which I'll do, but I'm posting here just to understand why this happens (not worrying if what I'm doing is good or not, just doing it for learning in this case).