Comment by nick__m

for mariadb :

0) make sure the the database data volume is on lvm or zfs

in a sql prompt:

  1) BACKUP STAGE START; BACKUP STAGE BLOCK_COMMIT;
  2) \! the shell command to take the snapshot
  3) BACKUP STAGE END;

you can now mount your snapshot, copy it offsite and delete it. The restore procedure is left as an exercise!