From: Marc Eshel <eshel@almaden.ibm.com>
Subject: Re: [patch] lockd control of grace period for HA NFS
Date: Tue, 30 Nov 2004 09:03:34 -0800
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References: <20041130155507.5DBD11BB00@citi.umich.edu>
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Cc: andros@citi.umich.edu, Neil Brown <neilb@cse.unsw.edu.au>,
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        Trond Myklebust <trond.myklebust@fys.uio.no>
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To: "William A.(Andy) Adamson" <andros@citi.umich.edu>
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William A.(Andy) Adamson wrote on 11/30/2004 07:55:07 AM:

> The NFSv4 portion looks ok to me; I'm lockd ignorant :-)

> To migrate a client from NFSv4 server1 to NFSv4 server2 both exporting a
> shared file system, the administrator will perform the following tasks

> 1) expire the client on NFSv4 server1 (remove the in-memory client state)
> 2) turn on (toggle) the grace period for all NFSv4 servers exporting the
> shared file system
> 3) change the mount on the client from NFSv4 server1 to NFSv4 server2.

I would do step 2 first to make sure that the client doesn't lose any locks
in the window between step 1 and 2.
I hope that when we are done the administrator will not have to do anything
on the client machines but instead the fs-location/moved will be used to
redirect the client from one server to another.

> While in the grace period, all NFSv4 servers will deny all non-recalim
OPEN
> and LOCK requests. READ/WRITE/SETATTR(file size change) on existing or
> reclaimed OPEN/LOCK will succeed. So, when an NFSv4 client migrates from
one
> NFSv4 server to another NFSv4 server (both exporting a shared file
system),
> *all* non-reclaim OPEN/LOCK request from any client will stall with
> NFS4_ERR_GRACE.

> I just completed a patch to allow READ/WRITE/SETATTR(file size change)
while
> in the grace period for existing/reclaimed state.

> I'm currently working on the stable storage portion of the NFSv4 server
> reclaim.

> -->Andy

>
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