Messages in this thread | | | Date | Tue, 1 Sep 2009 16:01:21 +0200 | From | Pavel Machek <> | Subject | Re: MD/DM and barriers (was Re: [patch] ext2/3: document conditions when reliable operation is possible) |
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On Thu 2009-08-27 12:54:05, Jeff Garzik wrote: > On 08/27/2009 09:10 AM, Ric Wheeler wrote: >> One thing that does need fixing for some MD configurations is to stress >> again that we need to make sure that barrier operations are properly >> supported or users will need to disable the write cache on devices with >> volatile write caches. > > Agreed; chime in on Christoph's linux-vfs thread if people have input. > > I quickly glanced at MD and DM. Currently, upstream, we see a lot of > > if (unlikely(bio_barrier(bio))) { > bio_endio(bio, -EOPNOTSUPP); > return 0; > } > > in DM and MD make_request functions. > > Only md/raid1 supports barriers at present, it seems. None of the other > MD drivers support barriers.
Not even md/raid0? Ouch :-(.
Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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