Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have a couple of servers serving exactly the same content through NFS to several webfarms, all the servers involved are running CentOS 5

The content between both NFS servers is replicated using Unison (tried drbd in the past, killed the performance badly)

To distribute load I'm mounting a different NFS server from each of the farms.

  • Webfarm1 mounts NFS1
  • Webfarm2 mounts NFS2

The only problem I have is when one of the servers crashes I would like to automatically remount the content from the other NFS server until the server recovers and then returns to the first server after a grace time.

Before I start writing such application I would like to know if there's any Opensource solution already available that does something close to what I'm intending, all the intelligence of the application should be on the client side (server side solutions have all been tested and discarded (heartbeat, drbd, etc...) since I want to use both NFS servers in an active-active solution.

Also it should be important that all servers in a webfarm are hitting the same NFS server, otherwise I would incur in some nasty replication issues.

Thanks beforehand for your help!

share|improve this question
up vote 2 down vote accepted

Have a look at the RedHat Cluster Suite NFS Cookbook, subtitled "Setting up a Load­Balanced NFS Cluster with Failover Capabilities". I think this may have some good suggestions, if it's not exactly what you're looking for.

You can take the ideas presented in that document and implement them using Pacemaker/Corosync, which I find much easier to work with than the legacy RedHat cluster tools.

You're basically asking for an active/active cluster with automatic failover. Since you're serving out from two independent -- but synchronized -- copies of the data, you've actually sidestepped most of the complicating issues that crop up (involving locking and other state synchronization) if you're actually trying to create a load-balancing NFS front-end to some sort of shared storage (e.g., a cluster filesystem like GFS).

share|improve this answer
Thanks larsks, at the end I'll end up running some version of GFS over a cabinet but right now I have to expand the lifetime of these two servers, I'll have a look at this! – lynxman Jan 29 '11 at 17:42
If you do have plans to run NFS on top of GFS, there's a lot of good reading in RedHat's bugzilla. E.g., this search. – larsks Jan 29 '11 at 17:45

You could use CTDB to do that. It supports NFS with correct file locking behaviour and lock recovery. Also, it is an active-active solution i.e. all NFS servers are active at the same time and the clients access them via service IP addresses (DNS round-robin) which can move from server to server in case of a node failure.

However, it a) is a server-side solution and b) requires a cluster filesystem like e.g. GPFS or GFS (which OTOH could be an advantage in comparison to your unison solution).

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.