SAM-QFS x.x Planning - Functional Specification Document
        ========================================================
                        Updated: 03/27/2008


FEATURE DESCRIPTION:  
-------------------

Add  the ability to mark a SAM-QFS client on or off in the QFS
file system client host table.  Clients that are marked as off
will only be able to unmount QFS file systems.  The purpose of
this feature is to enable the removal of a client from the HPC
SAM-QFS environment for repair or reconfiguration from a
central administrative point (the metadata server).

6479428: RFE: Functionality needed for Dynamic removal of a Shared QFS node


SCOPE OF THE PROJECT: 
--------------------

- Update commands and daemons that process the client host table.
- Modify the in-core client host table.
- Modify the samfs module so that it knows about and correctly handles
  the on/off state in the in-core client host table.
- Make the metadata server (MDS) allow only unmount-related messages
  from a client that has been marked "off."
- Make the MDS attempt to inform the client that has been marked "off"
  of this change if the client still has the file system mounted.
- Make the client that has been marked down attempt to unmount the
  file systems from that MDS that marked it down.

All other aspects of client host table management are outside the scope
of this feature.


FUNCTIONAL REQUIREMENTS:
-----------------------

A configuration file exists already per file system.  This file
contains a line per host and describes several parameters per
client host.  This file is in /etc/opt/SUNWsamfs/hosts.{fsname}.
Changes to this file are made effective by issuing the
"samsharefs" administrative command.  This existing interface
will be used to add an on/off flag per client host.  The 4th
column in this file is currently unused and will be used to
indicate host on/off status.

The host file is kept in memory once read via the samsharefs
command.  This host table will also have to change to accomodate
a new on/off flag per client.

The default status for a client will be "on".  If a client is
changed to "off" status, the following actions will be taken.
The metadata server (MDS) will accept no further commands from
that client other than "unmount".  The client will attempt to
flush and unmount all file systems from that metadata server.

Interfaces:

No interfaces are introduced or deleted by this proposal.  The
existing /etc/opt/SUNWsamfs/hosts.{fsname} configuration file
is modified to add the client on/off field.  The existing
samsharefs command will reread this file after changes.  This
interface is public/volatile.


DELIVERABLES: 
------------

- Restructure the in core and on disk host tables.

FUNCTIONAL DEPENDENCIES:
-----------------------

This requires that voluntary and involuntary failover be reliable prior to
integration of this feature.