Can you clarify, do you need two boxes with NFS as clustered resource or ?
For snapshots and stuff (outside cloud provider), ZFS filesystem should offer the same, if used on NFS server as filesystem.
There is also an options of LVM snapshots.
You can use it on open solaris implementations such as OmniOS or modern linux with openzfs implementation.
OpenZFS
This is what is proven and working.
There is BRTFS as well as a GPL COW filesystem, with snapshots, which i cannot suggest, since i'm not sure if it is mature enough for production usage.
Regards
Peasant.