Subject: Re: Fwd: Filesystem Questions
To: None <>
From: Bill Sommerfeld <>
List: netbsd-users
Date: 07/07/2000 10:34:56
> I have looked through your site and I could not find enough information
> regarding File Systems.  I know that FreeBSD uses UFS.  I got the
> impression that NetBSD uses FFS and can use LFS(journaling?)

What FreeBSD calls "UFS" and NetBSD calls "FFS" are essentialy the
same filesystem format (see the "A Fast Filesystem For Unix"
paper by McKusick et al, reprinted in, among other places, the
System Manager's Manual part of the O'Reilly 4.4BSD documentation set).

> I really want to know what the advantage of FFS is over UFS 

They're essentially the same filesystem.

> and how stable is LFS at this point in the game.  

The LFS implementation in NetBSD-current has been improving
significantly in stability over the past year, thank to the work of
Konrad Schroeder; however, it's still regarded as less stable and less
robust than FFS.

> I'm really interested in a journaling system.  

LFS is a "log structured" filesystem based on the Sprite
log-structured filesystem.  it differs from a "journalling filesystem"
in that the *entire* filesystem is kept in the log.
> Basically, I really want to try out NetBSD as I have heard many good things.
> I am a Linux user and I have used BSD based systems in the past(only thru
> telnet).  I want the speed and reliability that come with
> journaling.  

Note that ffs, unlike the linux implementation of ext2fs, has very
high reliability, because it enforces strict ordering on metadata
writes, albeit at some cost in performance. 

A recent change, "soft dependancies" (aka "softdeps") which is in
NetBSD-current and will be in the forthcoming NetBSD 1.5 release,
changes how write ordering is maintained to provide much of the same
performance advantages as journalling, and gives performance
comparable or sometimes even higher than filesystems running with
totally asynchronous metadata writes.

> which of these provide journaling?

> can journaling be installed when the OS is installed or is it patched on
> after the base system is installed?

LFS and FFS are two different filesystem formats; you can pick which
one to use on a partition by partition basis.  Currently, the install
tools only support using FFS format at install time; if you want to
experiment with LFS, reserve some disk space at install time and
reformat it after install as LFS.

					- Bill