Date: Mon, 26 Jul 2004 13:52:19 -0400 From: Brian Fundakowski Feldman <green@freebsd.org> To: Scott Long <scottl@freebsd.org> Cc: bugghy <bugghy@home.ro> Subject: Re: magic sysrq keys functionality Message-ID: <20040726175219.GA96815@green.homeunix.org> In-Reply-To: <20040726114142.E32601@pooker.samsco.org> 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>
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On Mon, Jul 26, 2004 at 11:49:55AM -0600, Scott Long wrote: > On Mon, 26 Jul 2004, Brian Fundakowski Feldman wrote: > B> On Sun, Jul 25, 2004 at 09:23:36PM +0000, bugghy wrote: > > > Yeah but it sometimes "freezes" (no reboot) ... and I'd rather umount my > > > filesystems before rebooting. > > > > SoftUpdates guarantess that your file systems will not get corrupt. > > > > This isn't entirely correct. Softupdates guarantees that you won't get > corruption due to metadata pointing to invalid or stale data blocks. > That's not the same as guaranteeing that there won't be any corruption. > Write caching on the drive combined with an in-opportune power loss or > other failure can easily leave you with corrupt or incomplete metadata > and/or data blocks. A panic while metadata is being committed to disk can > also leave the metadata highly inconsistent and prone to corruption. > This isn't to say the SU is bad or that other strategies are necessarily > better, just that there are definite risks. 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." I don't particularly think not having UPS is a good idea, but those can fail, and even so the ordering is such that a truncated inode won't result in a truly corrupt filesystem, and the inode doesn't get written until its contents are written out. Also, hw.ata.wc really shouldn't default to 1. -- Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\ <> green@FreeBSD.org \ The Power to Serve! \ Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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