On Mon, 2002-06-24 at 18:23, Alexander Shaw wrote: > Hey I was close, thanks for that. > > So when exactly does it happen? > > > > On Mon, 24 Jun 2002, Alexander Shaw wrote: > > > > > I'm a fairly new Linux user and in a quiet moment I suddenly > > thought about > > > defragmenting the drives on my RH 7.2 server. I did a search of > > the net and > > > from what I have read am I correct in assuming that > > defragmentation is an > > > integral part of the kernel and it happens automatically? > > > > yup, although you're better off describing it as an integral part > > of the ext2 filesystem.
The kernel does no defragging job, nor does the ext2 filesystem itself. What really happens is that the ext2 filesystem is designed in such a way as to prevent fragmentation from building up in the first place. I'm not a filesystem hacker myself, but from what I've read I can tell you that the system takes the following measures: * When allocating disk space, the filesystem allocates several block at once to increase the amount of contigous blocks belonging to a file. Under light disk load conditions, there is no noticeable effect, but under heavy disk load, when there are lots of processes requesting filesystem space, it gets allocated more contiguosly to each file. * When creating files, the filesystem code tries to spread them as evenly as possible (within performance constraints) across the filesystem space. This gives files room to grow contiguosly untill the filesystem approaches 100% capacity. Despite these measures, a filesystem can get fragmented. You can check the fragmentation of a filesystem with 'e2fsck -n -f /dev/whatever'. If you try it on a mounted filesystem, disregard the errors that will appear, since they are meaningless on a mounted filesystem. Also note that this takes a long time on large filesystems. There is a tool to defrag ext2 filesystems whose name I don't remember right now, but the techniques described above make it mostly unneeded. Finally, make a note that these comments only apply to the ext2 and ext3 filesystems. Other filesystems behave differently. I hope these helps you better understand the fragging issues in linux. Cheers, -- Javier Gostling Ingeniero de Sistemas Virtualia S.A. [EMAIL PROTECTED] Fono: +56 (2) 202-6264 x 130 Fax: +56 (2) 342-8763 Av. Kennedy 5757, of 1502 Las Condes Santiago Chile _______________________________________________ Redhat-list mailing list [EMAIL PROTECTED] https://listman.redhat.com/mailman/listinfo/redhat-list
