Mirroring disk between computers

I want to have a logical disk (using LVM) that is mirrored between two computers. That is, I want one filesystem that has complete copies on two different computers. I want to do this on Linux, preferably without significant add-ons. Ideally, I would like to be able to access it from either computer, locally, and NFS publish it for other machines. One solution might be to publish the "disk" on one machine with iSCSI or network block device (NBD) or the like, use RAID mirroring on that, then a filesystem, and then NFS to share it with everyone. This does everything but local access (but can be reconfigured if the normal master is dead), and is easily extended to more machines. Another might be two independent filesystems synced by cron jobs running rsync. What I am hoping for is an advanced distributed filesystem solution, that can also merge changes if one node is disconnected, edited, and reconnected. **Edit**: The basic requirements: I currently keep all my network management information on one computer. Every so often, it has trouble booting. (It is so old, the battery has died (and the big storm last Thursday (Maine) took out power).) So I would like to automatically distribute the data around to other machines in the network, so that as long as one works, I can get it all.