Trond Myklebust wrote:
On Wed, 2006-05-24 at 13:58 -0400, Jeff Moyer wrote:
==> Regarding [autofs] Re: [NFS] Re: [RFC] Multiple server selection and replicated mount failover; Trond Myklebust <trond.myklebust@xxxxxxxxxx> adds:
trond.myklebust> On Wed, 2006-05-24 at 13:05 +0800, Ian Kent wrote:
4) How does NFS v4 fit into this picture as I believe that some
of this functionality is included within the protocol.
And this.
NFS v4 appears quite different so should I be considering this for v2 and
v3 only?
trond.myklebust> NFSv4 has full support for migration/replication in the
trond.myklebust> protocol. If a filesystem fails on a given server, then
trond.myklebust> the server itself will tell the client where it can find
trond.myklebust> the replicas. There should be no need to provide that
trond.myklebust> information at mount time.
And what happens when the server disappears?
There are 2 strategies for dealing with that:
Firstly, we can maintain a cache of the list of replica volumes (we can
request the list of replicas when we mount the original volume).
This assumes a lot on the part of the server and it doesn't seem to me
that current server implementations are ready with the infrastructure to
be able to make this a reality.
I think that the client should be prepared to handle this sort of scenario
but also be prepared to take a list of servers at mount time too.
Secondly, there are plans to add a backup list of failover servers in a
specialised DNS record. This strategy could be made to work for NFSv2/v3
too.
This would seem to be a solution for how to determine the list of replicas,
but not how the NFS client fails over from one replica to the next.
Thanx...
ps
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