brian@fog.ann-arbor.mi.us (Brian S. Schang) (11/08/90)
Please excuse my ignorance, but I have a few questions... I understand that A/UX 2.0 is able to run two different file systems. I believe that one is the standard System V, and the other choice is the Berkeley Fast File System? Is this correct? Assuming the above is correct, what are the differences between the two? What are the advantages of each? I've gotten the impression that FFS is better, is this true? Why? Why would I not want to run it? Are the two compatable and able to be mounted simultaneously? Sorry about the abundance of vague questions. I will be installing A/UX 2.0 on another drive soon (hopefully), and I would guess that that would be a good time to switch from Sys V to FFS if this move is desirable. Thanks a *lot*! -- Brian S. Schang N8FOG brian@fog.ann-arbor.mi.us 46131 Academy Drive schang@caen.engin.umich.edu Plymouth, MI 48170-3519
rmtodd@servalan.uucp (Richard Todd) (11/09/90)
brian@fog.ann-arbor.mi.us (Brian S. Schang) writes: >I understand that A/UX 2.0 is able to run two different file systems. >I believe that one is the standard System V, and the other choice >is the Berkeley Fast File System? Is this correct? Yep. >Assuming the above is correct, what are the differences between the >two? What are the advantages of each? I've gotten the impression >that FFS is better, is this true? Why? Why would I not want to run >it? Are the two compatable and able to be mounted simultaneously? System V filesystem is basically the same as the old Version 7 filesystem (with only minor changes--block size 1K instead of 512 bytes, things like that). It shares the same limitation as V7 in that file names are limited to 14 chars; also, the System V/V7 filesystem doesn't make much of an attempt to avoid fragmentation. The BSD FFS (Fast File System) attempts to do a better job at allocating files to avoid fragmentation; this means that the disk head doesn't have to seek as much to find all the pieces of your file, so file accesses are more efficient. BSD filesystem also allows you to have filenames with >14 chars (the limit is 255, I believe). (For those curious on just how the BSD FFS makes file I/O faster, the chapter on it in the book _The Design and Implementation of the BSD4.3 Operating System_ by Leffler et al. will probably tell you more than you wanted to know :-) So, BSD FFS filesystems are more efficient (my not-terribly-rigorous tests showed roughly a factor of 3 speed increase on my Miniscribe 9380S drive), and allow you to have longer filenames. You can have both System V and BSD- style filesystems mounted simultaneously with no problem. The only possiblereason you'd want to leave a filesystem as SysV is if converting it would be a big hassle (e.g. it's a 100M+ filesystem and you don't have a tape drive to do dump/restore onto so you gotta use floppies :-) >Sorry about the abundance of vague questions. I will be installing >A/UX 2.0 on another drive soon (hopefully), and I would guess that >that would be a good time to switch from Sys V to FFS if this move >is desirable. It's an excellent time to do the switchover, since you're backing everything up anyway (or at least you *should* be backing everything up :-). -- Richard Todd rmtodd@uokmax.ecn.uoknor.edu rmtodd@chinet.chi.il.us rmtodd@servalan.uucp