I was thinking of mirroring a couple of directories across a number of (Linux) servers on my local network.
Google gave me this article. But it is almost 10 years old. So, I image the state-of-the-art may have changed a bit.
I would appreciate an update. Are there any new alternatives?
check on their git and release pages if they are still active ,
you should know before what you want to deploy , shared block storage ( e.g. a virtual disk ) like ceph or drbd , or a shared filesystem , like glusterFS / globalFS
recommendation: use glusterfs with bit-rot and 3+ machines :
Obviously it depends on your requirements, but consider also SyncThing.
You will have to manually indicate the private IP directions of the peers to your nodes as (currently, for updates see here) only the public IP gets automatically announced by SyncThing. EDIT: Syncthing now announces the private IP also (in a secure way) as implemented here so there's no need to manually specify it.