From: Brandon Simmons Subject: [NFS] Very Slow Sequential Reads over NFS from an XFS disk in Amazon EC2 Date: Thu, 11 Mar 2010 16:40:39 -0500 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: nfs@lists.sourceforge.net Return-path: Received: from neil.brown.name ([220.233.11.133]:52703 "EHLO neil.brown.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754825Ab0CKVqv (ORCPT ); Thu, 11 Mar 2010 16:46:51 -0500 Received: from brown by neil.brown.name with local (Exim 4.71) (envelope-from ) id 1NpqDR-0007xT-KQ for linux-nfs@vger.kernel.org; Fri, 12 Mar 2010 08:46:49 +1100 Sender: linux-nfs-owner@vger.kernel.org List-ID: I am using tiobench to test performance of an NFS mounted volume, and notice that Sequential Reads are much slower than Random Reads. This isn't the behavior when I run the same test on the disk mounted locally. For random reads I'm getting: 50 MB/s over NFS v.s 384 MB/s when mounted locally This is in comparison to the benchmark for _Random Reads_, in which I get: 288 MB/s both over NFS _and_ when directly mounted The other benchmarks seem to be in line with what I would expect, but I'm fairly new to NFS. Why would sequential reads over NFS be sooo much slower than random reads over NFS? I am exporting the volume on the server like this /export *.internal(no_subtree_check,rw,no_root_squash) and mounting with this: mount -o hard,intr,async,noatime,nodiratime,noacl $NFS_SERVER:/export /nfs Additionally I am doing all this in amazon EC2, exporting an EBS volume with the XFS file system (redundant, I know). I have tried using jumbo frames and various other mount options, but none seem to have much effect. Thanks for any clues. ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs _______________________________________________ Please note that nfs@lists.sourceforge.net is being discontinued. Please subscribe to linux-nfs@vger.kernel.org instead. http://vger.kernel.org/vger-lists.html#linux-nfs