From: Chuck Lever Subject: Re: [NFS] NFS Digest, Vol 18, Issue 70 (NFS performance problems) Date: Wed, 21 Nov 2007 11:04:55 -0500 Message-ID: <47445727.5090705@oracle.com> References: <47434ED7.4010100@redhat.com> <47435049.1010800@redhat.com> Reply-To: chuck.lever@oracle.com Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------080308050100050607040009" Cc: Peter Staubach , Wendy Cheng , nfs@lists.sourceforge.net To: Wendy Cheng Return-path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list2-new.sourceforge.net with esmtp (Exim 4.43) id 1Ius5m-0001vv-Gc for nfs@lists.sourceforge.net; Wed, 21 Nov 2007 08:06:22 -0800 Received: from rgminet01.oracle.com ([148.87.113.118]) by mail.sourceforge.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.44) id 1Ius5q-0003ET-3g for nfs@lists.sourceforge.net; Wed, 21 Nov 2007 08:06:28 -0800 In-Reply-To: <47435049.1010800@redhat.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: This is a multi-part message in MIME format. --------------080308050100050607040009 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Hi Wendy- Wendy Cheng wrote: > Peter Staubach wrote: >> Wendy Cheng wrote: >>> >>>> top - 15:50:56 up 20 days, 1:33, 9 users, load average: 3.42, >>>> 2.95, 2.38 >>>> >>>> 19200 geo0501 15 0 75076 5224 3480 S 2 0.1 0:07.94 >>>> smbd 2336 root 10 -5 0 0 0 S 1 >>>> 0.0 57:07.70 kjournald 2334 root 10 -5 0 >>>> 0 0 S 1 0.0 33:19.89 kjournald 2279 root 10 >>>> -5 0 0 0 S 0 0.0 15:10.98 md0_raid1 2283 >>>> root 10 -5 0 0 0 S 0 0.0 24:45.79 >>>> md1_raid1 3935 root 15 0 0 0 0 S 0 >>>> 0.0 14:04.25 nfsd 3943 root 15 0 0 >>>> 0 0 S 0 0.0 14:18.43 nfsd 3947 root 15 >>>> 0 0 0 0 S 0 0.0 13:57.06 nfsd 8325 >>>> ed0127 15 0 75044 4812 3264 S 0 0.1 0:01.29 >>>> smbd >>> Intuitively (based on ext3's journal threads info above) I would >>> suspect this is due to the change of the export default option from >>> "async" to "sync" between 2.6.9 and 2.6.18 kernels. So go to your >>> /etc/exports file and explicitly set the export option to "async" to >>> see whether you can get the performance back. >>> >>> e.g. changes "/server *(rw)" to "/server *(async, rw)". >> While this may or may not restore your performance aspects, it >> is not safe to make this change. The change was made for a >> reason. > > Not to start a flame war :) but please read his email. His *old* system, > that uses "async" option", has been running fine for several years. Why > all of sudden, an "async" option is such a big issue ? That means his old system would have been exposed to data corruption issues if it crashes (panic, power outage, etc). Using "sync" became default because async is inherently careless about data integrity. The data loss is often entirely silent. This is explained in the Linux NFS FAQ, question B6. See http://nfs.sourceforge.net/index.php#faq_b6 It's another case of where we perform better in older kernels but we are more correct in recent kernels... but our users don't appreciate the correctness improvement :-) > -- Wendy >> Please any and all other possibilities before making this change. >> It is not free. It's a reasonable *experiment* to try adding the "async" export option. That would identify the source of the performance loss. It's almost never a good choice to use "async" in production. --------------080308050100050607040009 Content-Type: text/x-vcard; charset=utf-8; name="chuck.lever.vcf" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="chuck.lever.vcf" begin:vcard fn:Chuck Lever n:Lever;Chuck org:Oracle Corporation;Corporate Architecture: Linux Projects Group adr:;;1015 Granger Avenue;Ann Arbor;MI;48104;USA email;internet:chuck dot lever at nospam oracle dot com title:Principal Member of Staff tel;work:+1 248 614 5091 x-mozilla-html:FALSE version:2.1 end:vcard --------------080308050100050607040009 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ --------------080308050100050607040009 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ 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 --------------080308050100050607040009--