From: Bruce Allan Subject: Re: slow NFS performance extracting bits from large files Date: Mon, 16 Dec 2002 09:27:49 -0800 Sender: nfs-admin@lists.sourceforge.net Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: nfs@lists.sourceforge.net, nfs-admin@lists.sourceforge.net Return-path: To: Bruce Allen 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: Hi Bruce (good name, btw), It would help if you posted information about your network. Alternately, you could read the "Optimizing NFS Performance" section of the Linux NFS-HOWTO located at http://nfs.sourceforge.net/nfs-howto/ Regards, --- Bruce Allan Software Engineer, Linux Technology Center IBM Corporation, Beaverton OR 503-578-4187 IBM Tie-line 775-4187 Bruce Allen cc: Bruce Allen Sent by: Subject: [NFS] slow NFS performance extracting bits from large files nfs-admin@lists.sour ceforge.net 12/15/2002 11:02 PM 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 ------------------------------------------------------- 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