使用非外部卷是在dockerized postgres中持久保存数据的好方法

Question

After reading

How to persist data in a dockerized postgres database using volumes

I know mount a volume to local host folder, is a good way to prevent data loss, in case fatal happens in docker process.

I'm using Windows as host and Linux based docker image. Windows is having problem to mount postgres data (Linux based docker image) to Windows host directory - Mount Postgres data to Windows host directory

Later, I discover another technique

  postgres:
    build:
      context: ./postgres
      dockerfile: Dockerfile
    restart: always
    ports:
      - "5432:5432"
    volumes:
      - postgres_data:/var/lib/postgresql/data

volumes:
  postgres_data: {}

I can use a non external volume (I have no idea what is that yet)

After implement such, I try to perform

docker-compose down
docker-compose up

The data is still there.

May I know,

1. Is this still a good way to persist data in dockerized postgres?
2. Where exactly data is being stored? Is it some hidden directory in host machine?

Answer 1

1. Is this still a good way to persist data in dockerized postgres? no but olso yes ....postgres is DB so data should be externalized to avoid data-loss in case of connection failure to the container etc...

But a good practice would be to have 2 DB 1 on containers 1 on host or in 2 containers (then with data inside containers) in master/slave mode synchro to have high availability for container maintenance for example but this is high availability only not backup ! :) if it doesn't exist you have to create it of course :-)

2. Where exactly data is being stored? Is it some hidden directory in host machine?

No it is where you share the /var/lib/postgres so in your example in a directory called postgres_data on host

(use full path is a good practice & then you saw/guess by yourself where it was define in your file) :)