NFSv4 namespace extensions

Introduction

The NFSv4 spec (RFC 3530) defines how a server maintains a pseudo-filesystem namespace linking the filesystems it shares, so that clients can navigate to them from the server root.  Many clients rely on this "server namespace" to be able to access all filesystems on the server transparently.  The Solaris NFS client does not yet do this because we have had the benefit of the Solaris automounter, but especially when using ZFS, it is unpleasant to be unable to see new filesystems without updating and propagating the automounter maps.  This project plans to deliver "mirror mounts" to cross over server filesystem boundaries and do mounts transparently on demand, without interfering with automounter operation.

The NFSv4 spec and a supporting draft also defines a means for a server to inform a client that data it seeks lives at another location; this is called a "referral", and referrals can be used to construct an enterprise namespace. This project will deliver the ability for the client to follow referrals and mount filesystems transparently on demand.

Status

We have putback the mirror-mount part of this OpenSolaris project. It is available in snv_77.

We took a mirror-mounts prototype and a referrals prototype to Connectathon 2007 and had good end-to-end success with both.  After that, we have unified the prototypes into one and revised some of the internal interfaces.  We then
put the project on hold to focus on other activities.

In April 2009, we found a way to fund referrals work again, and have a client-side prototype that leverages the automatic unmounting and trigger
vnode code from mirror mounts, and a server-side prototype that reads
referrals out of extended attributes.  Work is going on to do something
smarter than extended attributes.

Documents

New! Our requirements documents are posted here:

<http://opensolaris.org/os/project/nfs-namespace/files/mm-PRS-open.html>

<http://opensolaris.org/os/project/nfs-namespace/files/ref-PRS-open.html>

Code Access
(coming soon)

Testing

Test Plan <http://opensolaris.org/os/project/nfs-namespace/files/mm-TP-open.html>

Test Assertions
<http://opensolaris.org/os/project/nfs-namespace/files/mm-test-assertions.txt>

Discussions

As you can see on our Discussions page, we will discuss this work on nfs-discuss@opensolaris.org until traffic levels justify our own alias.