General question about Database, Recorder, history

Hi, folks,
I started with HassIO two weeks ago and i like it very much. I’m using version 0.81.2
My instance is installed on a Rasperry Pi 3 B+ with 64GB SD-Card.
As I read, it’s recommended to use an external Database if one intends to store sensor-values ​​over a long period of time. So i installed influxdb (v 1.6.4) on a separate Machine running Ubuntu 18.04.
In my configuration.yaml i defined:

influxdb:
  host: !secret ip_influxdb
  database: !secret name_influxdb
  max_retries: 3
  default_measurement: nounit
  exclude:
    domains:
      - automation
      - sun
      - zone
      - device_tracker
      - group
    entities:
      - sensor.cpu_load_total
      - sensor.memory_usage_real
      - sensor.network_down
      - sensor.network_up
      - sensor.status_smart_sda
      - sensor.total_size_volume_1
      - sensor.wetter_symbol
  include:
    domains:
      - sensor

I watched communication on the network and everything works fine.
New values of included sensors appear in the database, with wireshark i can see, “write” commands which transfer data from hassio to influxdb.
What i do not understand:
I never saw a “read” command on the wire, as i expected e.g. when clicking on a sensor value to show the history of this entity (the last 24 hrs).
My question: are the values (displayed in the line graph, for example of a humidity sensor,) stored in both databases but taken from the sqliteDB on the raspberry only, when they are displayed in sensor history of a card?

Thx in advance
Max

This is correct. Influxdb is write only. You can create a Influxdb sensor if you want to read a value.

@gpbenton Many Thanks for the quick response!
I’m thinking about using Grafana to display graphs for the (in influxdb included) long term entities, so i hope the raspberry never reaches the limits of the SD-Card, but i don’t know where the limit of 24 hours is set and/or if I need to set any (other) limitation for the internal database on the Raspi!?