On Thu, May 20, 1999 at 09:23:45PM +0400, Oleg Polyanski wrote:
> >>>>> "Manuel" == Manuel Bouyer writes:
> 
> >> good news are here. the story
> >> 
> >> http://www.news.com/News/Item/Textonly/0,25,36807,00.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	                                      tls@rek.tjls.com
	"And where do all these highways go, now that we are free?"