How to ensure file synchronization between VPS (without using cdn)?

Question

linux

There is one instance of the application that works with the database and accepts, saves files, and also gives them away.
We need to deploy it in another region, the replica database has been set up, the instance has been raised, but the application does not yet work with cdn.
What is the best way to quickly synchronize files between vps, what tools to resolve, are there already precedents and examples? And so that there are no cyclic records: server1 -> server2 -> server1 -> ... so that it registers on the server once

Answer 1

syncthing - daemon, hangs in memory, synchronizes files between a bunch of clients. at small changes in a file - updates only changed. read the same rsync only smarter.
about terabyte clouds were cast on lore from a dozen and a half clients.
Inotify keeps track of writing to disk, so it catches disk changes almost immediately.
web face control.
open source

Answer 2

ceph, glusterfs.

Answer 3

The simplest rsync is s1->s2 and s2->s1 a cron once a minute.
It's fast and cheap and with a lot of points: sync time is once a minute, space usage on both servers.
Better yet (for the future) read OnYourLips

Answer 4

Nginx reverse proxy and configure cache in it

Answer 5

rsync to cron