Date: Thu, 21 Sep 2000 12:24:20 -0400 (EDT) From: Craig A Soules <soules+@andrew.cmu.edu> To: freebsd-fs@freebsd.org Cc: freebsd-fs <freebsd-fs@FreeBSD.ORG> Subject: Re: Journaling Filesystems in bsd? (LFS, anyone?) Message-ID: <wtmXMoK00UwCIZndEl@andrew.cmu.edu> In-Reply-To: <Pine.BSF.4.21.0009210738440.11353-100000@orvieto.eecs.harvard.edu> References: <Pine.BSF.4.21.0009210738440.11353-100000@orvieto.eecs.harvard.edu>
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Excerpts from internet.computing.freebsd.fs: 21-Sep-100 Re: Journaling > Log-structured file systems offer different semantics than > synchronous journaling file systems. Synchronous journaling can > offer the traditional durability of create. Nothing is durable Wouldn't it be possible to offer the same semantics as FFS in an LFS implementation if the segment was (over)written after each operation? I'm not sure what sort of performance penelty you would incur for this behavior, although it would probably depend heavily upon the segment size. Although with a 64kb segment size, the penelty would probably be small, since its overhead isn't much higher than the 8kb block write seen by a synchronous journaling system. In fact, this might be more efficient than journaling in the long run, since you wouldn't have dirty data building up in the cache. Of course, there is that read thing... > Does the cleaner work? (always the first question to ask when people > talk about their LFS implementations). This may be wrong, so don't flame me, but... I had heard that there was no fully working implementation of LFS in the *BSDs for this reason (and in fact there was an LFS branch in FreeBSD as well, but it was removed since the cleaner was in such shoddy shape). craig To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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