GlusterFS

It is a very common problem that you need a filesystem that is synced between several computers and stays available, even if some servers are down. Here is a nice overview of those filesystems https://en.wikipedia.org/wiki/Comparison_of_distributed_file_systems

https://en.wikipedia.org/wiki/Gluster#GlusterFS is one of those filesystems.

Install

https://www.osradar.com/install-and-configure-glusterfs-debian-10/

On each server:

apt install glusterfs-server
systemctl start glusterd
systemctl status glusterd

On any server probe all the other servers

gluster peer probe thorsten-gluster-test-2.example.com
gluster peer probe thorsten-gluster-test-3.example.com
...

Plus one server also needs to add to first one

gluster peer probe thorsten-gluster-test-1.example.com

This lists all the servers but yourself

gluster peer status

This lists all the server

gluster pool list

Create a volume, list all the servers and where on the server the data should be stored

gluster volume create my-glusterfsvolume replica 3 \
  thorsten-gluster-test-1.example.com:/mnt/my_gulsterfs_test \
  thorsten-gluster-test-2.example.com:/mnt/my_gulsterfs_test \
  thorsten-gluster-test-3.example.com:/mnt/my_gulsterfs_test
gluster volume start my-glusterfsvolume

Mount a volume (this is a stupid way as it only works when this server is online while you mount)

mount -t glusterfs thorsten-gluster-test-1.example.com:/my-glusterfsvolume /mnt/my_gulsterfs_test/ -o backupvolfile-server=thorsten-gluster-test-2.example.com