Re: mismatch_cnt again

From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Bill Davidsen <davidsen@tmr.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
	Peter Rabbitson <rabbit+list@rabbit.us>,
	NeilBrown <neilb@suse.de>,
	Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>,
	Goswin von Brederlow <goswin-v-b@web.de>,
	Doug Ledford <dledford@redhat.com>,
	Michael Evans <mjevans1983@gmail.com>,
	Eyal Lebedinsky <eyal@eyal.emu.id.au>,
	linux-raid list <linux-raid@vger.kernel.org>
Subject: Re: mismatch_cnt again
Date: Tue, 17 Nov 2009 00:19:40 -0500	[thread overview]
Message-ID: <yq1hbstd8yb.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <4AFEE283.9040702@tmr.com> (Bill Davidsen's message of "Sat, 14 Nov 2009 12:01:55 -0500")

>>>>> "Bill" == Bill Davidsen <davidsen@tmr.com> writes:

>> FWIW, databases on raw disk have gone out of fashion.  But it is true
>> that applications that do direct I/O need to avoid updating buffers
>> in flight.
>> 

Bill> May have gone out of fashion in new applications (I'm not sure I
Bill> agree, but as a talking point), 

I don't believe Oracle supports it anymore.  ASM solves this and several
other problems.

Bill> but there are tons of old apps which are not going to be updated
Bill> any time soon, and any number of libraries which mmap stuff and
Bill> effect multiple applications.

We'll just unmap the page while it's being written out.

-- 
Martin K. Petersen	Oracle Linux Engineering