Return-Path: Received: from mail-iw0-f176.google.com ([209.85.223.176]:42537 "EHLO mail-iw0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934119Ab0CLSXM convert rfc822-to-8bit (ORCPT ); Fri, 12 Mar 2010 13:23:12 -0500 Received: by iwn6 with SMTP id 6so1033188iwn.4 for ; Fri, 12 Mar 2010 10:23:11 -0800 (PST) In-Reply-To: References: From: Brandon Simmons Date: Fri, 12 Mar 2010 13:22:51 -0500 Message-ID: Subject: Very Slow Sequential Reads over NFS from an XFS disk in Amazon EC2 To: linux-nfs@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 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.