Date: Wed, 23 Apr 1997 15:33:52 +1200 From: physmsa AT cantua DOT canterbury DOT ac DOT nz (Mr M S Aitchison) Subject: File Systems (was Re: Usage of directory entries To: alaric AT abwillms DOT demon DOT co DOT uk, opendos-developer AT delorie DOT com Message-id: <199704230333.PAA26913@cantua.canterbury.ac.nz> Precedence: bulk > > Fragmentation can be solved by moving fragmented files (found when the filer > > notes that accessing a certain file has entailed a lot of extent seeks) into > > contiguous areas from time to time, a sort of background defrag that works > > on individual files when it feels the need. > Slooow! It seems really slow! I have to agree. Win95 does that. Perhaps because the heads aren't left near where they're most often wanted, or because FAT partitions never get ver fast anyway. I'd prefer to have a filesystem that isn't so subject to fragmentation so a defragger has little to do. What I would like the system to do (as an option; if you have enough RAM, etc) is to record what files are often needed after other files, to sensibly preload or rearrange sectors. I think the priorities should be: (1) Decide on a system (lets call it IFS) to which filesystem-dependent drivers can be added (with the least source changes from Linux the better!) This should be able to be used on generic DOS (albeit with some limitations) but certainly tie in with OpenDOS security. (2) Start with at least ext2fs and vfat drivers for it. (3) Invite others (especially commercial/shareware vendors of existing hpfs, etc drivers) to write using it. Make sure the licencing allows them to distribute the IFS with their product to help it become popular. (4) Design "automatic" diskette and CDROM drivers that adapt to the media formats, e.g. detecting Macintosh diskettes. So the IFS should start by doing a simple check "is this a valid FAT diskette", and even "does this have a known virus signature or characteristics of viruses?", then call each loaded driver until one recognises the format. (5) Design a totally new file system that requires very little RAM yet is efficient (to be very efficient it might want more RAM), and capable of storing just about any extended attributes, ACL permissions, etc. If anybody wants to discuss details I have some ideas (which I'd love to simulate, if anybody has flexible software for the job). ------------------------------------------------------------------------------- Mark Aitchison, Physics & Astronomy \_ Phone : +64 3 3642-947 a.h. 3371-225 University of Canterbury, (/' "per haps ad gloria" -------------------------------------------------------------------------------