This is part of The Pile, a partial archive of some open source mailing lists and newsgroups.
Subject: Re: Linux and Dos FS -- A question From: Ramon Gandia <rfg@nook.net> Date: Tue, 04 May 1999 02:03:20 +0000 Benjamin Sher wrote: > > Dear friends: > > Just wondering: > > Since Linux allows you to create either a Dos or Linux file system and > save your data (apparently any date of any sort) either on a > Dos-formatted floppy or Zip or a Linux-formatted floppy or Zip, what's > the difference (other than the obvious that a Dos-formatted Zip or > floppy can be shared with other OS? Is there any qualitative, intrinsic > difference that would make me want to favor one FS over another in > saving my data (executable, docs, images, audio files, etc.)> The MSDOS filesystem is composed of a directory and a FAT table with a duplicate (spare FAT table) immediately adjacent. Roughly, on the very first track of the first cylinder (track 0, side 0, cylinder 0) you have sector 1. Sector 1 has the Master boot record. The following several sectors contain the directory and the FAT tables. For the most part, any problems with this track will leave the floppy in an unusable state. The duplicate FAT table does not make the disk readable by DOS, but may allow limited repair with a repair utility program. In contrast, the Unix ext2 filesystem has inode tables. The "directory" resides in the inode table. This is a series of ganged pointers at the data on the disk. There are several inode tables on the disk, and if one is damaged, ANY of the others will do. For this reason, damage to a particular track or sector will not knock the ext2 filesystem. You will get a bunch of error messages, but running efsck will repair it. This is far more robust than the MSDOS filesystem. The downside is that there is more disk space in overhead than in MSDOS: you get less data on a Linux disk. Be aware that due to the entry in /etc/fstab, you probably are not getting efsck checking your floppies. You can end up with a badly damaged floppy that still seems to work okay, and you are fat and dumb about it. You should manually run efsck on your floppies once in a while, specially your critical ones. You do this to an UNMOUTED floppy. There are two programs: efsck and e2fsck (I think). Oner is generic and there is an option for ext2; the other is specific to ext2. Its really a shortcut to the first one. Contrary to your experience, I have *never* lost a Linux floppy. I have had some with errors, but in every case I was able to pull the data off from it....or at least some data, without resorting to heroic efforts or a disk sector editor like is necessary sometimes in DOS. There are better file systems yet. When they get really robust they begin to suffer from speed problems and storage space problems. It is not likely you will see anything better than ext2 used for a FLOPPY, but you certainly can for hard drives, specially in enterprise servers where reliability is always more important than speed or space. ====