From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul Smith" Subject: Re: NFS client write performance issue ... thoughts? Date: 06 Jan 2004 01:33:29 -0500 Sender: nfs-admin@lists.sourceforge.net Message-ID: References: <16378.15074.348051.673492@guts.uio.no> Reply-To: "Paul Smith" Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Return-path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.11] helo=sc8-sf-mx1.sourceforge.net) by sc8-sf-list2.sourceforge.net with esmtp (Exim 4.24) id 1Adkmb-00088C-Fb for nfs@lists.sourceforge.net; Mon, 05 Jan 2004 22:33:41 -0800 Received: from zrtps0kp.nortelnetworks.com ([47.140.192.56]) by sc8-sf-mx1.sourceforge.net with esmtp (Exim 4.30) id 1Adkmb-0003lY-22 for nfs@lists.sourceforge.net; Mon, 05 Jan 2004 22:33:41 -0800 Received: from zrtps0m6.us.nortel.com (zrtps0m6.us.nortel.com [47.140.192.58]) by zrtps0kp.nortelnetworks.com (Switch-2.2.6/Switch-2.2.0) with ESMTP id i066XWG02977 for ; Tue, 6 Jan 2004 01:33:32 -0500 (EST) Received: from lemming.engeast.baynetworks.com (mail@lemming.engeast.baynetworks.com [47.17.140.90]) by zrtps0m6.us.nortel.com (Switch-2.2.6/Switch-2.2.0) with ESMTP id i066XU004148 for ; Tue, 6 Jan 2004 01:33:30 -0500 (EST) Received: from psmith by lemming.engeast.baynetworks.com with local (Exim 3.36 #1 (Debian)) id 1AdkmQ-00043s-00 for ; Tue, 06 Jan 2004 01:33:30 -0500 To: nfs@lists.sourceforge.net In-Reply-To: <16378.15074.348051.673492@guts.uio.no> Errors-To: nfs-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: Discussion of NFS under Linux development, interoperability, and testing. List-Post: List-Help: List-Subscribe: , List-Archive: %% Trond Myklebust writes: tm> P=E5 m=E5 , 05/01/2004 klokka 17:11, skreiv Paul Smith: >> Hi all; we've been doing some examination of NFS client performance, a= nd >> have seen this apparently sub-optimal behavior: anyone here have any >> comments on this observation or thoughts about it? tm> Does your observation include numbers, or is it just conjecture? Note I'm only forwarding comments I've received from another party, who's actually doing the investigation. The application in question is not GDBM but rather ClearCase; I guess there's some concern that the performance of ClearCase over NFS from a Linux client seems to be noticeably less than from a Solaris client. ClearCase uses a (heavily) customized version of the Raima database to store its internal information. I'll see if I can get any numbers. tm> The Solaris approach is only a win in the particular case where tm> you are doing several non-contiguous writes into the same page tm> (and without any byte-range locking). Note that like Linux, two tm> processes that do not share the same RPC credentials still cannot tm> merge their writes since you cannot rely on them having the same tm> file write permissions. In this particular case that's fine since the ClearCase database is only ever modified by one process on one system. tm> Looking at your particular example of GDBM, you should recall that tm> Solaris is forced to revert to uncached synchronous reads and writes tm> when doing byte range locking precisely because their page cache tm> writes back entire pages (the ugly alternative would be to demand that tm> byte range locks must be page-aligned). tm> OTOH Linux can continue to do cached asynchronous reads and writes tm> right up until the user forces an fsync()+cache invalidation by tm> changing the locking range because our page cache writes are not tm> required to be page aligned. Of course I don't have the source and I haven't sniffed the packets personally so I don't know exactly what goes on, but it's quite possible that the ClearCase implementation doesn't attempt to do any byte-range locking at all, since they pretty much know that there is only one process reading and writing the DB. The reason for using NFS involves maintenance, backup, reliability, etc. etc. (the NFS server is actually an EMC or NetApp NAS solution), not necessarily file sharing, at least insofar as the DB itself is concerned. Thanks for the reply, Trond; I'll see if I can get more concrete details and let you know. --=20 ---------------------------------------------------------------------------= ---- Paul D. Smith HASMAT--HA Software Mthds & To= ols "Please remain calm...I may be mad, but I am a professional." --Mad Scient= ist ---------------------------------------------------------------------------= ---- These are my opinions---Nortel Networks takes no responsibility for them. ------------------------------------------------------- This SF.net email is sponsored by: Perforce Software. Perforce is the Fast Software Configuration Management System offering advanced branching capabilities and atomic changes on 50+ platforms. Free Eval! http://www.perforce.com/perforce/loadprog.html _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs