From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Mon, 17 Jul 2006 03:36:30 -0700 (PDT) Received: from larry.melbourne.sgi.com (larry.melbourne.sgi.com [134.14.52.130]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with SMTP id k6HAa2DW020958 for ; Mon, 17 Jul 2006 03:36:14 -0700 Message-ID: <44BB592E.1040400@melbourne.sgi.com> Date: Mon, 17 Jul 2006 19:32:30 +1000 From: David Chatterton Reply-To: chatz@melbourne.sgi.com MIME-Version: 1.0 Subject: Re: file system defragmentation References: <4f52331f050826001612f8e323@mail.gmail.com> <20050826101131.GA24544@ii.uib.no> <4f52331f0508260848782f240a@mail.gmail.com> <43128F82.4010004@tlinx.org> <4312913F.6040205@coremetrics.com> <43311567.3060208@tlinx.org> <5356806.post@talk.nabble.com> In-Reply-To: <5356806.post@talk.nabble.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-To: xfs-bounce@oss.sgi.com List-Id: xfs To: Cosmo Nova Cc: linux-xfs@oss.sgi.com Cosmo Nova wrote: > Hi, you mentioned delayed allocation. What is the size of the buffer holding > the data, before they're actually written to disk? How can it tackle growing > files? I'll leave the details for Nathan/Dave... > > If I have a DVR system of 16 channels. They keep writing data to the disk in > pieces of video files. I read some spec of xfs. Apart from extend-based > allocation, there're allocaiton groups in xfs. I would like to ask, does > XFS's allocation groups work similar as JFS's, which would lock an > allocation group for individual file write? How does the allocation group in > XFS work? And how would it help the fragmentation problem? > Locking down an allocation group is part of what a new "filestream" mount option will provide. This feature is already in use at a number of IRIX sites with media apps (mainly in conjunction with CXFS since you have more writers in a clustered filesystem and more need to lock down contiguous space), and is coming to Linux XFS soon. The best way to tackle fragementation with streaming data is to preallocate space for the files. This allows the allocator to try to find the space you require using as large contiguous chunks as it can find. See xfsctl(3). David -- David Chatterton Phone: +61 3 9963 1934 XFS Engineering Manager Mobile: +61 409 154 121 SGI Australia http://www.sgi.com/products/storage