[ale] Fileserver/filesystem replication

[Matt Smith]

Does anyone have experience with any filesystem replication methods other than rsync alone?  I'm looking for something a little more real-time (preferably not scheduled) to do at a minimum a one-way replication to a "backup" server, and ideally, a two-way replication so that two servers could be used in parallel.

I realize the former could be accomplished with a frequently scheduled rsync, but I'm hoping for something a little more robust than that.  I can tolerate a one-way copy to the backup server as long as it's done very quickly after a file is modified, because if I ever have to fail over to the backup server for reads, it probably means the primary is down hard so I won't have to worry about copying updates to it any time soon.  I'm handling the failover via a NFS connection through a F5 Load balancer that will point the connections to the primary server unless it's down...

I've looked into coda, several clustering filesystems: pvfs, and a few others (some commercial, but I've got no budget for this, of course), but they all seem to either lack the nonscheduled replication I'm looking for, or are more focused on parallel access than replication for fault tolerance.

Thanks in advance for any feedback on your experiences.

--Matt