Date: Sat, 22 Jun 1996 12:03:01 -0700 (PDT) From: Gary Kline <kline@tera.com> To: jmb@freefall.freebsd.org (Jonathan M. Bresler) Cc: anneb@svl.tec.army.mil, kline@tera.com, black@mr.net, questions@freebsd.org Subject: Re: LFS anyone? Message-ID: <199606221903.MAA16245@athena.tera.com> In-Reply-To: <199606212004.NAA22850@freefall.freebsd.org> from "Jonathan M. Bresler" at "Jun 21, 96 01:04:42 pm"
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According to Jonathan M. Bresler: > Anne Brink wrote: > > > > > According to Ben Black: > > > Seems like the LFS would make fsck's obsolete. Yes? No? > > > > > > Yes, LFS does some rollbacks after a crash, BUT, the file system is not > > checked. It's just assumed to be fine. Fsck actually does verify that you > > LFS works forward from a 'checkpoint' to reconstruct the filesystem > in the event of a crash. at the time the checkpoint was written > the filesystem was stable and consistent. there are two checkpoint > regions on disk, the active checkpoint toggles back and forth between > the two. the last item written to disk is the toggle. > > > like syslogs and mail logs and things like that. If you have lots of random > > file accesses, especially over NFS which caches things in blocks, not whole > > files, you may lose a /lot/ of the LFS functionality, and possibly get worse > > performance than with FFS. The LFS model isn't consistent with the concept > > of cylinder groups, but uses the theory of locality which helps its efficiency. > > As for a regular user file system? Well, I'd want to run some benchmarks. (-; > > memory, memory, memory. for LFS to be effective on general purpose > uses, you must have enough memory to satisfy a very large percentage > of reads from the (now unified vm and ) file cache. > > at least this is my understanding of LFS, i may be wrong > i imagine that i will find out ;) > Interesting stuff. For my own system, or for any system, data integrity is the critical issue. Memory is cheap (or at least reasonable); getting more so. gary (dreaming of those 4GB SIMM's :-) >
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