Date: Fri, 22 Jan 1999 11:46:28 +0100 (CET) From: Konrad Heuer <kheuer@gwdu60.gwdg.de> To: Robin Huiser <R.Huiser@Winthesis.com> Cc: "'freebsd-questions@freebsd.org'" <freebsd-questions@FreeBSD.ORG> Subject: Re: Disk fragmentation and FreeBSD Message-ID: <Pine.BSF.3.96.990122112819.19332A-100000@gwdu60.gwdg.de> In-Reply-To: <E12964702DD4D011A39D00805FE44CE5190AEB@ARAGORN>
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On Fri, 22 Jan 1999, Robin Huiser wrote: > I am a using Microsoft NT Server/workstation (please read further!! :-) ) > and I was wondering why MS NTFS suffers of extreme fragmentation while my > FreeBSD 2.2.6 server (which has the same amount of disk/file changes as the > NT Server) has a fragmentation level of 0.6 %. (NTFS: 100 % according to > Diskkeeper). > > What makes the difference, and... are there even any defrag tools for > FreeBSD. (I don't need them, just curious!). I don't know many details about NTFS; I will limit myself to FreeBSD and FAT: FreeBSD uses the Berkeley Fast Filesystem (FFS). The usage of the term `fragmentation' concerning FFS is very different from what is expected by someone who is accustomed to the DOS/Windows FAT filesystem. Fragmentation in the FAT system means the arbitrary spreading of data blocks over the disk after a long time of operation. The result is limited performance. You surely know about that. The FFS doens't significantly suffer from that kind of fragmentation as long as there enough free space (about 10% of total space) in the file system since the block allocation algorithms are excellent. In the FFS, file data may be stored not only in total disk blocks (usually 8K), but also in fragments of a block (usually 1K). To be precise, the last data block may be allocated imcomplete (one or more fragments). This is to prevent wasting of disk space by small files. For example, 8 files each less than 1K are stored altogether in one disk block. Thus, the rate of fragmentation of a FFS has to do with the ratio of allocation of fragements and blocks. Regards // // Konrad Heuer ____ ___ _______ // Gesellschaft für wissenschaftliche / __/______ ___ / _ )/ __/ _ \ // Datenverarbeitung mbH GÖttingen / _// __/ -_) -_) _ |\ \/ // / // Am Faßberg, D-37077 GÖttingen /_/ /_/ \__/\__/____/___/____/ // Deutschland (Germany) ----- The Power to Serve ----- // http://www.freebsd.org // kheuer@gwdu60.gwdg.de // To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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