Subject: Re: SGI will freely license its XFS
To: Oleg Polyanski <>
From: Thor Lancelot Simon <>
List: current-users
Date: 05/24/1999 09:36:56
On Thu, May 20, 1999 at 09:23:45PM +0400, Oleg Polyanski wrote:
> >>>>> "Manuel" == Manuel Bouyer writes:
> >> good news are here. the story
> >> 
> >>,25,36807,00.html
> >> 
> >> tells that SGI will release the source code of their XFS. it lacks some
> >> features but is able to handle with files of very big size, has b-tree
> >> layout on the media and, the most important, it is journaling file
> >> system. if the license is acceptable I guess it will quite easy to port
> >> XFS into NetBSD.
> Manuel> How is it different from our LFS ?
> 	they are very different. xfs is an ordinary (but extremely optimized
> for high speed data access) journaling file system and stores the transaction 
> log somewhere on the disk (in other slice of disk or in the slice of another
> disk or inside the filesystem itself). lfs is a log-structured file system,
> there is no transaction log or data - file system itself is a log. lfs is
> good in many terms but unfortunately it is write only file system; data
> reading without notable performance impact is impossible. lfs is an example
> of excellent research work but in real life it is unusable.

That's a huge oversimplification and, really, a false assertion.

I used LFS on Sprite for years.  NetApp NFS servers use something very, very
similar today.  I use our LFS today on machines I use for my daily work.  I
assure you that LFS is not "unusable".

I posted references here for several papers on improving LFS read performance,
particularly when cleaning, about two months ago.

Thor Lancelot Simon	                            
	"And where do all these highways go, now that we are free?"