From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id o0BHOMDT164305 for ; Mon, 11 Jan 2010 11:24:23 -0600 Received: from web76214.mail.sg1.yahoo.com (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with SMTP id BF12A159A85 for ; Mon, 11 Jan 2010 09:25:16 -0800 (PST) Received: from web76214.mail.sg1.yahoo.com (web76214.mail.sg1.yahoo.com [124.108.115.162]) by cuda.sgi.com with SMTP id sEhBpavREnQdYHK7 for ; Mon, 11 Jan 2010 09:25:16 -0800 (PST) Message-ID: <614476.89961.qm@web76214.mail.sg1.yahoo.com> Date: Tue, 12 Jan 2010 01:25:14 +0800 (SGT) From: Gim Leong Chin Subject: allocsize mount option MIME-Version: 1.0 List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: xfs@oss.sgi.com Hi, Mount options for xfs allocsize=size Sets the buffered I/O end-of-file preallocation size when doing delayed allocation writeout (default size is 64KiB). I read that setting allocsize to a big value can be used to combat filesystem fragmentation when writing big files. I do not understand how allocsize works. Say I set allocsize=1g, but my file size is only 1 MB or even smaller. Will the rest of the 1 GB file extent be allocated, resulting in wasted space and even file fragmentation problem? Does setting allocsize to a big value result in performance gain when writing big files? Is performance hurt by a big value setting when writing files smaller than the allocsize value? I am setting up a system for HPC, where two different applications have different file size characteristics, one writes files of GBs and even 128 GB, the other is in MBs to tens of MBs. I am not able to find documentation on the behaviour of allocsize mount option. Thank you. Chin Gim Leong New Email names for you! Get the Email name you've always wanted on the new @ymail and @rocketmail. Hurry before someone else does! http://mail.promotions.yahoo.com/newdomains/sg/ _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs