From: Bruce Allen Subject: slow NFS performance extracting bits from large files Date: Mon, 16 Dec 2002 01:02:55 -0600 (CST) Sender: nfs-admin@lists.sourceforge.net Message-ID: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Bruce Allen Return-path: Received: from uwm.edu ([129.89.7.2] ident=root) by sc8-sf-list1.sourceforge.net with esmtp (Exim 3.31-VA-mm2 #1 (Debian)) id 18NpHK-0000F8-00 for ; Sun, 15 Dec 2002 23:03:02 -0800 Received: from dirac.phys.uwm.edu (dirac.phys.uwm.edu [129.89.57.19]) by uwm.edu (8.12.6/8.12.6) with ESMTP id gBG72uMn026005 for ; Mon, 16 Dec 2002 01:02:56 -0600 (CST) To: nfs@lists.sourceforge.net Errors-To: nfs-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Id: Discussion of NFS under Linux development, interoperability, and testing. List-Unsubscribe: , List-Archive: I've searched/browsed the mail archive and the online documentation but am still a bit clueless about where to start. I am working on a scientific data analysis application which needs to extract a little bit of data from around 10,000 files. The files themselves are each around 1 MB in size. The application does: for (i=0; i<10000; i++){ open() ith file read() 32 bytes from beginning lseek() to somewhere in the middle of the file read() 620 bytes from the middle of the file close() ith file } If I run this with the data set on a local disk, the total run time is around 1 sec -- very reasonable since I am transferring around 6 MB of data. If I run this on an NFS-mounted disk the performance is 100 times worse. Both client and server are stock RH 7.3. Note that if I run it a second time, when the data is presumably cached, it takes just a few seconds to run. Is it obvious what needs to be changed/tuned to improve this performance? Or if not, could someone suggest a tool and a strategy for tracing down the cause of the poor performance? Sincerely, Bruce Allen ------------------------------------------------------- This sf.net email is sponsored by: With Great Power, Comes Great Responsibility Learn to use your power at OSDN's High Performance Computing Channel http://hpc.devchannel.org/ _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs