Date: Mon, 17 Apr 2000 13:12:44 +0200 (CEST) From: Rasmus Skaarup <rasmus@gal.dk> To: Alfred Perlstein <bright@wintelcom.net> Cc: Rasmus Skaarup <rasmus@gal.dk>, freebsd-questions@FreeBSD.ORG Subject: Re: disc io - sync and async Message-ID: <Pine.BSF.4.21.0004171300150.10236-100000@skaarup.org> In-Reply-To: <20000416120315.W4381@fw.wintelcom.net>
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[Mounting devices] > > - Why is sync mode more secure? (I was told that a recovery would be less > > painful if drives are mounted in sync mode - in case of a breakdown.) > > It's not 'sync' it's 'non-async', a 'sync' mount means that no caching > is done, a 'non-async' mount means that meta-data operations are done > 'sync'. > > Please see: http://www.ece.cmu.edu/~ganger/papers/CSE-TR-254-95/ This presumably increases perfomance, but why isn't such a patch default for FreeBSD? (Or is this already implemented?) > > - Why does a simple 'mount' command tell me that both sync and async reads > > and writes are being performed on me FreeBSD box? > > Because it looks cool? :) If async operations are performed anyhow, why don't we just mount the drives async from the beginning. If FreeBSD chooses to mount drives in sync or 'non-async' mode as you say, to increase integrity, and async operations are performed anyway this doesn't help one bit. You still have problems with integrity, and the drives will just be slower.. Surely we should avoid any kind of breach in integrity, but I mean, a server breakdown is what it is, and having 200 inodes instead of 300 inodes corrupted doesn't sound like a worthy result of a much slower hard drive when the server is up. And even if FreeBSD only performed sync operations, there would still be some parts of the filesystem that are corrupted? Maybe I've got it all on backwards, but I've never given much thought to ufs - it's allways worked for me :-) Best regards Rasmus To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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