-storage. A snapshot will be made of the container volume, and the
-snapshot content will be archived in a tar file.
+storage. First, the container will be suspended to ensure data consistency.
+A temporary snapshot of the container's volumes will be made and the
+snapshot content will be archived in a tar file. Finally, the temporary
+snapshot is deleted again.
+
+NOTE: `snapshot` mode requires that all backed up volumes are on a storage that
+supports snapshots. Using the `backup=no` mountpoint option individual volumes
+can be excluded from the backup (and thus this requirement).
+
+NOTE: bind and device mountpoints are skipped during backup operations, like
+volume mountpoints with the backup option disabled.