From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Sun, 25 May 2008 08:38:53 -0700 (PDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.168.29]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m4PFcoOU005647 for ; Sun, 25 May 2008 08:38:50 -0700 Received: from sandeen.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 597F41AFC7A for ; Sun, 25 May 2008 08:39:40 -0700 (PDT) Received: from sandeen.net (sandeen.net [209.173.210.139]) by cuda.sgi.com with ESMTP id JCPF4pyFnMz5XiHL for ; Sun, 25 May 2008 08:39:40 -0700 (PDT) Message-ID: <48398839.6060304@sandeen.net> Date: Sun, 25 May 2008 10:39:37 -0500 From: Eric Sandeen MIME-Version: 1.0 Subject: Re: XFS for lots of small files References: <4820832B.3070903@dubielvitrum.pl> <200805062055.36755.Martin@lichtvoll.de> <4838DC1A.5010206@sandeen.net> (sfid-20080525_131427_063047_18AAAB7D) <200805251338.48910.Martin@lichtvoll.de> In-Reply-To: <200805251338.48910.Martin@lichtvoll.de> Content-Type: text/plain; charset=ISO-8859-2 Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Martin Steigerwald Cc: linux-xfs@oss.sgi.com Martin Steigerwald wrote: > Am Sonntag 25 Mai 2008 schrieb Eric Sandeen: >> Martin Steigerwald wrote: >>> And there is quite some fragmentation on it: >>> >>> xfs_db> frag >>> actual 653519, ideal 587066, fragmentation factor 10.17% >> No, there's not. > > OK, so there is or better was (see below) *some* fragmentation. > >> You have 653519 extents out of an "ideal" 587066. >> >> That is 653519/587066 = 1.113 extents per file. >> >> It is not "quite some" fragmentation, it is near perfect (although this >> is subjective, and also depends on the size of your files... if they >> are all 8k then 1.113 extents per file might be a bit high; if they >> average 1G then 1.113 extents on average is pretty darned good.) > > They vary a lot. From KMail ~/Mail directory with hundred of thousands of > mails in maildir format to a picture and movie collection from various > digicams with 150KB over 2-4 MB to 50-200 MB in size and a music > collection and kernel sources and and and... would need to run a tool on > them to gather some statistic. > > Anyway, nothing that can't be optimized: Sure... I'd just argue that it's diminishing returns :) > shambala> xfs_db -r /dev/sda5 > xfs_db> frag > actual 683648, ideal 617593, fragmentation factor 9.66% > xfs_db> quit > > shambala> xfs_fsr /dev/sda5 > /home start inode=0 > > shambala> xfs_db -r /dev/sda5 > xfs_db> frag > actual 620316, ideal 617584, fragmentation factor 0.44% > xfs_db> quit > > xfs_fsr copied over several gigabytes and the free space of the partition > temporarily more than once was 4 GB less than the 20 GB of free space it > had before and after invoking xfs_fsr ;) fsr needs to preallocate space to "defragment into" so this is expected, temporarily. > Not that I noticed a difference up to now however. right, my original reply was meant to imply that fragmentation is not really a problem for you. :) And in the larger picture, I just wanted to point out that the "fragmentation factor" can be pretty misleading. It reports as (actual - ideal) / actual. Imagine a filesystem full of 8GB dvd iso images, each with 4 2GB extents. The fragmentation factor would be reported as (4X - 1X) / 4X = 75%. Which looks "bad," but really isn't. -Eric