On Sun 2009-01-04 17:06:34, Theodore Tso wrote: > On Sun, Jan 04, 2009 at 01:49:49PM -0600, Rob Landley wrote: > > > > Want to document the granularity issues with flash, while you're at it? > > > > An inherent problem with using flash as a normal block device is that the > > flash erase size is bigger than most filesystem sector sizes. So when you > > request a write, it may erase and rewrite the next 64k, 128k, or even a couple > > megabytes on the really _big_ ones. > > > > If you lose power in the middle of that, ext3 won't notice that data in the > > "sectors" _after_ the one your were trying to write to got trashed. > > True enough, although the newer SSD's will have this problem addressed > (although at least initially, they are **far** more costly than the > el-cheapo 32GB SD cards you can find at the checkout counter at Fry's > alongside battery-powered shavers and trashy ipod speakers). > > I will stress again, that most of this doesn't belong in > Documentation/filesystems/ext3.txt, as most of this is *not* > ext3-specific. I've initially done the patch for ext3 because that's what I'm using and becuase I felt responsible for documenting it after a huge thread. At least barrier=1 seems to be ext3 specific, and perhaps logfs or something can survive full eraseblocks disappearing. Anyway, i guess we all agree that this needs to be documented _somewhere_, and that's what I'm trying to do. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
