Re: [nfsv4] Some stuff on referrals/migration

Hi Dave,

I think we had a referrals/migration discussion a year or so
back, where there issue came down to some fundamentals of a
global namespace: should it be implemented at the client or
at the server.  Currently it's based at the client, via automounters,
and NFSv4 referrals are an attempt to base it at the server.
But I don't think we're going to resolve that here.

I think NFS4ERR_MOVED and fs_locations was proposed with a more
modest goal of allowing server admins to shuffle NFS filesystems
around and the back end and not have to tell the clients, i.e.
the clients would just automagically follow the referrals,
mounts could stay in place, and files stay open.  I believe
it was inspired by the AFS filesystem, which could quite
easily relocate filesystems on the fly via some clever
snapshotting and simple Volume Location Database updates.
However, I don't think NFS is anywhere near as monolithic
as AFS was, with its VLDB, cells, and special filesystems.

There are some issues that NFSv4 cannot have its own way,
and filesystem relocation is probably one of them.  How
do you make it work on a multi-protocol NAS server ?
How do the CIFS, AFP and NFSv2,v3 clients follow a filesystem
that's been moved ?  I just don't think file server admins
are going to move stuff around - unless there's some kind
of accomodation for existing NFS clients.

	Brent

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