Need suggestions for a R/W distributed file system for a webserver cluster running Apache+PHP

Solution 1:

The "Least Worst" (TM) option here is NFS. I know thats tough to swallow. I tried to avoid it with rsync, I've tried to avoid it with GFS, I've tried to avoid it with incron/inotify. I've tried to avoid it by pushing developers to stop using the filesystem as a datastore. In the end we really don't have a better option than NFS. Not because NFS is good, as you said the HA part of it is rough, but because there's really no better option.

Solution 2:

It's still technically 'beta' but Bittorrent Sync would be perfect for you I think. I don't have such an environment (multiple webservers) so haven't tried it myself, but have heard of others doing exactly this and been very happy. I do use it for distributed server backups, which is a similar use from a technical perspective: http://wandin.net/dotclear/index.php?post/2013/07/17/Distributed-server-backups-with-btsync

http://labs.bittorrent.com/experiments/sync.html