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Re: [Linux-cluster] NFS load balancing on REDHAT cluster

On Fri, 2005-09-09 at 13:37 +0200, Baesso Mirko wrote:
> Hi
> we have to setup a Redhat cluster with two node on an attached shared
> storadge system (Fibre Channel connection).
> We would like to know if is possible to setup an NFS service clustered
> with load balancing 

Personally, I haven't tried this, but here's my pseudo-educated guess...

It should be possible, but there may be some interesting issues with NFS
synchronization across the cluster (WRT statd, mountd synchronization).
I do not know if NFS will behave well as a load-balanced service.  In
theory, locking should work (because the NFS locks translate to GFS
locks, which would be cluster wide).  You'll probably want to
pre-populate /var/lib/nfs/rmtab with all the possible client entries on
each node.

You'll probably need to set up IPVS on a machine to do the load
balancing.  You can use piranha, one of the many other front ends to
IPVS, or just do it by hand.

You'll want to make sure that you group mountd+lockd+nfs(+portmap?)
ports together on the IPVS director so that client A always requests
everything from server B once the initial communication is established
(which would typically happen via portmapper or mountd).  Also, you
should probably use well-known ports for everything NFS/RPC related
instead of the portmapper, because there's a good chance that when using
the portmapper, the ports in use by mountd/lockd/nfsd/etc will be
different on each server - which would make it really difficult for IPVS
to correctly load balance it ;)

> We have to use GFS file system for sharing storadge data on both node,
> but have to setup GNBD also for exporting same file system to client
> network?

This shouldn't be necessary.  If you do a GNBD import on the clients,
the clients will need to be running GFS.  If you're doing an NFS export
from the servers, they can simply be running NFS.

-- Lon

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