Date: Tue, 27 Jul 2004 01:00:39 +0200 From: Matthias Andree <ma@dt.e-technik.uni-dortmund.de> To: Brian Fundakowski Feldman <green@freebsd.org> Cc: bugghy <bugghy@home.ro> Subject: Re: magic sysrq keys functionality Message-ID: <m3fz7ejrvs.fsf@merlin.emma.line.org> In-Reply-To: <20040726175219.GA96815@green.homeunix.org> (Brian Fundakowski Feldman's message of "Mon, 26 Jul 2004 13:52:19 -0400") References: <1090718450.2020.4.camel@illusion.com> <200407251112.46183.doconnor@gsoft.com.au> <1090790611.4628.1.camel@illusion.com> <20040726152151.GC1473@green.homeunix.org> <20040726114142.E32601@pooker.samsco.org> <20040726175219.GA96815@green.homeunix.org>
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Brian Fundakowski Feldman <green@freebsd.org> writes: > If you just want to generalize it, you can say that "SoftUpdates > guarantees that your file systems will not get corrupt due to just > software errors." Not quite - it suggests that softdep were immune to bugs in its own implementation, which it certainly is not (and isn't claimed in the first place). softdep is just "async but writing blocks in the right order to avoid corruption of the on-disk state". It assumes your writes execute in the order scheduled. If your drive reorders writes, you can save the extra effort and switch to async. Same service level: "complete reinstall if it goes wrong". > I don't particularly think not having UPS is a good idea, Depends on the service level required. I have seen few power outages at home, one of 110 mins, one of 45 mins, and one or two of 2 or 3 minutes in the past 15 years - in a city of c. 200,000 inhabitants in Western Germany. Not something that would cause me to buy UPS, some software or hardware bug is way more likely to nuke a file system here. > Also, hw.ata.wc really shouldn't default to 1. What has always bothered me about this is that this FORCES the write cache on even if the drive's manufacturer or user configured it to off outside FreeBSD, for instance with the manufacturer's floppy, there is no such thing as "use whichever the drive had configured". -- Matthias Andree Encrypted mail welcome: my GnuPG key ID is 0x052E7D95 (PGP/MIME preferred)
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