Date: Mon, 13 Dec 1999 18:38:50 -0600 (CST) From: Jay Nelson <noslenj@swbell.net> To: Mattias Pantzare <pantzer@ludd.luth.se> Cc: chat@FreeBSD.ORG Subject: Re: Log file systems? (Was: Re: dual 400 -> dual 600 worth it?) Message-ID: <Pine.BSF.4.05.9912131837110.388-100000@acp.swbell.net> In-Reply-To: <199912121124.MAA25648@zed.ludd.luth.se>
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Thanks for the reply and the references. Your answer _should_ be a FAQ. It would save the repeat questions. -- Jay On Sun, 12 Dec 1999, Mattias Pantzare wrote: >> >How similar is that to the log partition in SGI's XFS? There was no >> >restriction as to what spindle the log filesystem was placed. Quite to >> >the contrary, it was indicated using a separate drive on a separate >> >SCSI bus would help performance. >> >> XFS sounds a lot like AIX's JFS. Which raises the question: What is >> the connection between BSD's lfs, soft updates, SGI's XFS and AIX's >> jfs? Don't they all do essentially the same thing except for where the >> log is written? > >No. lfs is a logging filesystem. You only have a log that contains everything, >including all your files. The downside to this is that you have to have a >garbage collector that cleans deleted data from the log. The good thing is >that you never have to seek for writes. All writes are to the end of the log. >http://www.cs.berkeley.edu/projects/sprite/papers/ has some papers on lfs. > >A journaling filesystem is like a normal filesystem but you have a transaction >log that turns synchronous writes into a synchronous write to the log and a >asynchronous write to the normal filesystem. This avoids seeks when latency is >important. > >Soft updates do not have a log att all. Take a look at > http://www.ece.cmu.edu/~ganger/papers/CSE-TR-254-95/. > > >Lfs will not roll in the normal sense, it will simply discard the half done >write at the end of the log if there is one. > >Soft updates can't do rolling as there is no log. > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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