From: James Pearson Subject: Re: Text based mount options ignoring the preferred rwsize? Date: Wed, 09 Sep 2009 22:47:06 +0100 Message-ID: <4AA8225A.9060107@moving-picture.com> References: <4AA68AA4.7090606@moving-picture.com> <188B198A-A113-4CA7-940D-EFBD026CBDD2@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Cc: linux-nfs@vger.kernel.org To: Chuck Lever Return-path: Received: from mpc-26.sohonet.co.uk ([193.203.82.251]:52209 "EHLO moving-picture.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752484AbZIIVrF (ORCPT ); Wed, 9 Sep 2009 17:47:05 -0400 In-Reply-To: <188B198A-A113-4CA7-940D-EFBD026CBDD2@oracle.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Chuck Lever wrote: >> >> Should the kernel be setting rsize (and wsize) to 0 by default? > > > nfs(5) says: > > "If an [rw]size value is not specified, or if the specified [rw]size > value is larger than the maximum that either client or server can > support, the client and server negotiate the largest [rw]size value > that they can both support." > > So the text-based behavior is what is documented now. > > Does anyone know of a reason to use the server's "preferred" transfer > size rather than the largest size supported by both client and server? > Usually those are the same. In this case, the manufacturer of the NFS server recommends using 128Kb for rsize and 512Kb for wsize - although the maximum rsize it supports is 512Kb. I assume in their testing, these values have given optimal performance figures. The default behaviour with binary mount options when no [rw]size is to select these preferred values - which to me, makes sense - as by not giving a [rw]size, you are leaving it up the server to pick the 'best' values for you - which I guess in most (all other?) cases happen to be the maximum size. James Pearson