From: "Chuck Lever" Subject: Re: Performance Diagnosis Date: Tue, 15 Jul 2008 11:49:11 -0400 Message-ID: <76bd70e30807150849j22ffd428i5e647794289a2c82@mail.gmail.com> References: Reply-To: chucklever@gmail.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: linux-nfs@vger.kernel.org To: "Andrew Bell" Return-path: Received: from yw-out-2324.google.com ([74.125.46.30]:27024 "EHLO yw-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752722AbYGOPtV (ORCPT ); Tue, 15 Jul 2008 11:49:21 -0400 Received: by yw-out-2324.google.com with SMTP id 9so2613797ywe.1 for ; Tue, 15 Jul 2008 08:49:13 -0700 (PDT) In-Reply-To: Sender: linux-nfs-owner@vger.kernel.org List-ID: On Tue, Jul 15, 2008 at 11:34 AM, Andrew Bell wrote: > Hi, > > I have a RHEL 5 system that exhibits less than wonderful performance > when copying large files from/to an NFS filesystem. When the copy is > taking place, other access to the filesystem is painfully slow. I > would like to have the filesystem react well to small requests while a > large request is taking place. > > A couple of questions: > > Is this a reasonable expectation? Yes, but Linux NFS can't fulfill it. :-) There is currently only one RPC transport socket between client and server for each mount point. Large file copies (or similar operations) will queue a lot of I/O, so your small requests will take a while to get through the queued up writes or reads ahead of them. > Is this perhaps an I/O scheduling issue that isn't specific to NFS, > but shows up there because of the latency of my NFS setup? > > Is this most likely a client issue, a server issue or a combination? Well, if your server or network is slow, this kind of thing is more likely to happen. > Do you have recomendations on the best way to determine what is > happening? Are there existing tools to monitor active IO/NFS > requests/responses and any relevant queues? Yes, I wrote some Python tools that are still undocumented (ie you will likely have to read the Python source to figure out what they do). They were recently included in nfs-utils, but you can download them from: http://oss.oracle.com/~cel/linux-2.6/2.6.25/nfs-iostat and http://oss.oracle.com/~cel/linux-2.6/2.6.25/mountstats > > > Thanks for any info/ideas before I get in too deep :) > > -- > Andrew Bell > andrew.bell.ia@gmail.com -- Chuck Lever