Messages in this thread | | | Date | Mon, 31 Aug 2009 13:04:48 +0200 | From | Pavel Machek <> | Subject | Re: raid is dangerous but that's secret (was Re: [patch] ext2/3: |
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Hi!
> Actually, there is something the file system can do to make journaling > safe on degraded RAIDs: make the (checksummed) journal blocks equal to > the RAID stripe size. Or, equivalently, pad out to the RAID stripe > size each commit. > > This sometimes leads to awkward block sizes, but while writing > to any *one* stripe on a degraded RAID-5 endangers the others, you > can write to *all* of them with the usual semantics.
Well, that would work... but you'd also have to journal data, with the same block size. Not exactly fast, but at least safe...
> That's one thing I really like about ZFS: its policy of "don't trust > the disks." If nothing else, simply telling you "your disks f*ed up, > and I caught them doing it", instead of the usual mysterious corruption > detectec three months later, is tremendoudly useful information.
The more I learn about storage, the more I like idea of zfs. Given the subtle issues between filesystem and raid layer, integrating them just makes sense. Pavel
-- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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