From mboxrd@z Thu Jan  1 00:00:00 1970
From: Valdis.Kletnieks@vt.edu
Subject: Re: [dm-devel] Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md.
Date: Tue, 10 Jul 2007 19:40:00 -0400
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References: <18006.38689.818186.221707@notabene.brown> <18010.12472.209452.148229@notabene.brown> <20070528094358.GM25091@agk.fab.redhat.com> <5201e28f0705290225v14fdac44hb0382a4137a84d01@mail.gmail.com> <20070529220500.GA6513@agk.fab.redhat.com> <5201e28f0705300212g3be16464u5ee1a4c80db27a11@mail.gmail.com> <465DAC72.1010201@cfl.rr.com> <5201e28f0705310414u1a9aebc4je135748274543946@mail.gmail.com> <465F9197.7060002@gmail.com> <Pine.LNX.4.64.0705312144400.6705@asgard.lang.hm> <465FC7B1.3060309@gmail.com>
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In-Reply-To: Your message of "Tue, 10 Jul 2007 14:39:41 EDT."
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Cc: Tejun Heo <htejun@gmail.com>, david@lang.hm, Stefan Bader <Stefan.Bader@de.ibm.com>, Phillip Susi <psusi@cfl.rr.com>, device-mapper development <dm-devel@redhat.com>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, Jens Axboe <jens.axboe@oracle.com>, David Chinner <dgc@sgi.com>, Andreas Dilger <adilger@clusterfs.com>
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On Tue, 10 Jul 2007 14:39:41 EDT, Ric Wheeler said:

> All of the high end arrays have non-volatile cache (read, on power loss, it is a 
> promise that it will get all of your data out to permanent storage). You don't 
> need to ask this kind of array to drain the cache. In fact, it might just ignore 
> you if you send it that kind of request ;-)

OK, I'll bite - how does the kernel know whether the other end of that
fiberchannel cable is attached to a DMX-3 or to some no-name product that
may not have the same assurances?  Is there a "I'm a high-end array" bit
in the sense data that I'm unaware of?


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