Re: NFS Failover
On Wed, Jun 26, 2013 at 02:11:42PM -0400, David Parker wrote:
> I'm wondering if there is a way to set up a highly-available NFS share
> using two servers (Debian Wheezy), where the shared volume can failover if
> the primary server goes down. My idea was to use two NFS servers and keep
> the exported directories in sync using DRDB. On the client, mount the
> share via autofs using the "Replicated Server" syntax.
>
> For example, say I have two servers called server1 and server2, each of
> which is exporting the directory /export/data via NFS, and /export/data is
> a synced DRDB filesystem shared between them. On the client, set up an
> autofs map file to mount the share and add this line:
>
> /mnt/data server1,server2:/export/data
>
> This is close, but it doesn't do what I'm looking to do. This seems to
> round-robin between the two servers whenever the filesystem needs to be
> mounted, and if the selected server isn't available, it then tries the
> other one.
>
> What I'm looking for is a way to have the client be aware of both servers,
> and gracefully failover between them. I thought about using Pacemaker and
> Corosync to provide a virtual IP which floats between the servers, but
> would that work with NFS? Let's say I have an established NFS mount and
> server1 fails, and the virtual IP fails over to server2. Wouldn't there be
> a bunch of NFS socket and state information which server2 is unaware of,
> therefore rendering the connection useless on the client? Also, data
> integrity is essential in this scenario, so what about active writes to the
> NFS share which are happening at the time the server-side failover takes
> place?
>
> In full disclosure, I have tried the autofs method but not the
> Pacemaker/Corosyn HA method, so some experimentation might answer my
> questions. In the meantime, any help would be greatly appreciated.
http://www.howtoforge.com/high-availability-nfs-with-drbd-plus-heartbeat
is the story of how somebody did that. Ubuntu rather than
Debian, but you should be able to translate easily.
You are correct that NFS is going to be very unhappy with
stateful changes. What you actually need is to use a clustered
filesystem rather than NFS.
-dsr-
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