Date: Thu, 21 Sep 2000 11:18:47 -0400 From: Dwight Tuinstra <tuinstra@clarkson.edu> To: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: Journaling Filesystems in bsd? (LFS, anyone?) Message-ID: <39CA26D7.51D314BF@clarkson.edu> References: <9164771DDCABD3118333005004E9446E204774@mother.netcentralen.dk> <20001222152532.B97883@roaming.cacheboy.net>
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Adrian Chadd wrote:
>
> On Thu, Sep 21, 2000, Michael Aronsen wrote:
> > Hello
> > Just wanted to know if there are any projects to get something like reiserfs
> > to FreeBSD?
>
> There's a few ideas floating around but noone has provided anything
> concrete.
>
> You're more than welcome to start something more concrete. :-)
I'm interested in porting an alternative file system to FreeBSD.
As a long-term graduate research project, I've been looking into
the code for LFS (Log-structured File System) on NetBSD. Such a
system is optimized for many small writes, and given the amounts
of RAM available for read caches nowadays, should deliver read
performance comparable (or not much worse) than FFS. Additionally,
LFS should provide better and faster crash recovery than either FFS
or journaling file systems.
In a nutshell, the difference between journaling file systems
and LFSes is that jFSes keep a log of metadata, whereas an LFS
keeps metadata AND data in a unified log structure (and yes, this
means playing lots of tricks with how inodes are located and found).
At present, the only working, available LFS system (that I'm aware
of) for a freeNIX is the one in NetBSD, though there are at least two
efforts underway for Linux. There is an order of magnitude
improvement in the write times for their "pkgsrc" directory
(equivalent to the FreeBSD "ports" directory) when comparing
FFS to LFS. The NetBSD LFS code is still beta, but in pretty good
working order.
There has been controversy regarding the performance claims
of LFS under various disk activity patterns. The research I'll be
doing aims to investigate the claims, especially after implementing
the optimizations proposed by Matthews et al (Improving the
Performance of Log-Structured File Systems With Adaptive Methods;
Proc. Sixteenth ACM Symposium on Operating System Principles).
Dr. Matthews is my advisor on this research.
Is there any interest in porting/redesigning LFS for FreeBSD?
--Dwight Tuinstra
tuinstra@clarkson.edu
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