From: Chuck Lever <chuck.lever@oracle.com>
Subject: Re: NFS client request failure statistics?
Date: Mon, 04 Jun 2007 11:00:16 -0400
Message-ID: <46642900.5020502@oracle.com>
References: <20070602003340.GA5482@ifa.hawaii.edu>
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Cc: nfs@lists.sourceforge.net
To: Joshua Hoblitt <jhoblitt@ifa.hawaii.edu>
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Joshua Hoblitt wrote:
> Hello,
> 
> I was wondering if there is some existing means (systemtap, etc.) of
> getting a count of NFS client requests that have "failed" after
> exceeding the maximum number of retransmissions?

Only "soft" mounted NFS file systems will ever "fail" a request after 
some number of retransmits.  "hard" mounted NFS file systems will 
continue retrying forever.  See nfs(5) for more details on using these 
mount options.

The Linux NFS FAQ has some wisdom about why you shouldn't use "soft" 
mounts, but rather "hard,intr".

> I've spent a small amount of time poking around in the sources to see
> how difficult it would be export this information to userspace.  It
> appears that this would be non-trivial to do as it seems that the NFS
> client code itself doesn't keep a count of failed requests and the
> procfs interface (/proc/net/rpc/nfs) is auto-generated by the sunrpc
> layer.  Is my analysis correct?

The traditional statistics-keeping method is in /proc/net/rpc/nfs, but 
there is a new one that is exported in /proc/self/mountstats.  It 
wouldn't be challenging to add a stat there that counted soft requests 
that timed out.

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