I have 2 networks separated by a WAN (25/25 fiber optic VPN). I would like to provide some files to both servers on networks via NFS (and Samba for the desktops, but that's on a per-site basis). some of these files are core to the operation of the servers, so I would like some amount of redundancy between the two networks so that if the VPN link goes down, operations are not interrupted. there is no need for the synchronization of sites to be "instant", although I would prefer them to be quick instead of some sort of hourly
rysnc job. I'm also interested in scaling to 3-5 network sites at some point in the future, so growth is a consideration.
from my research so far, there seem to be a few options:
1) drbd for sync between sites and then NFS on each side
2) clustered NFS
3) homebrew solution using unionfs, rsync or similar
it seems like drbd is actually the simplest solution, which for some reason seems counter-intuitive to me. are there another solutions I haven't found in my searching?