Are backups taking all mysql database?

Operating system: 20.04 Ubuntu 18.04 16.04
OS version:
I just did a one old backup

root@kangarooo:/home/backup/backup2# tar -zxvf ./protesti.sql root@kangarooo:/home/backup/backup2# ls -lh protesti.sql -rw-rw-r-- 1 protesti protesti 70M Dec 13 2016 protesti.sql
a new backup

root@Latvijai:/mnt/volume_fra1_01/backup# tar -zxvf ./protesti.sql
root@Latvijai:/mnt/volume_fra1_01/backup# ls -lh protesti.sql
-rw-rw-r-- 1 1029 1029 70M Dec 13  2016 protesti.sql

and a mysqldump

mysqldump -u root -p protesti > protestidump.sql
root@Latvijai:/mnt/volume_fra1_01# ls -lh protestidump.sql
-rw-r--r-- 1 root root 901M Jan 10 22:48 protestidump.sql

Difference of 70-901MB

It does seem like an extreme example, but databases in general do compress quite a bit.