From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: RAID6 rebuild stuck Date: Wed, 3 Oct 2012 11:21:20 +1000 Message-ID: <20121003112120.67d16a3b@notabene.brown> References: <20121001112946.GB27455@nsrc.org> <20121002155642.606b2108@notabene.brown> <20121002155633.GC30589@nsrc.org> <506B45C3.4090902@anonymous.org.uk> <20121003062907.3886b2fd@notabene.brown> <506B4FF9.8070904@anonymous.org.uk> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/lTqH2o=nDgbJ.0oFOs=Xr1x"; protocol="application/pgp-signature" Return-path: In-Reply-To: <506B4FF9.8070904@anonymous.org.uk> Sender: linux-raid-owner@vger.kernel.org To: John Robinson Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/lTqH2o=nDgbJ.0oFOs=Xr1x Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 02 Oct 2012 21:35:05 +0100 John Robinson wrote: > On 02/10/2012 21:29, NeilBrown wrote: > > On Tue, 02 Oct 2012 20:51:31 +0100 John Robinson > > wrote: > > > >> On 02/10/2012 16:56, Brian Candler wrote: > >>> On Tue, Oct 02, 2012 at 03:56:42PM +1000, NeilBrown wrote: > >>>> Lesson: always do a read test as well as a write test! > >>> > >>> And there was me thinking that drives read back data after writing it= - > >>> clearly they do not :-) > >> > >> Would it be worth adding a re-read onto the end of the usual read > >> failure reconstruct-write cycle? > > > > What? Read twice? > > > > We already read after the write when attempting to fix a failure. >=20 > I didn't realise you already did that. >=20 > > I suspect it doesn't do much good though as the data is in cache in the= drive. >=20 > No, maybe not. There isn't an option you can add to ask for an uncached=20 > read? But I dare say you'd have thought of that already if there was :-) Maybe setting REQ_FUA would work. Or maybe it would cause crashes and rand= om data corruption. I suspect most people think of REQ_FUA as being associated with WRITEs. Maybe I'm to cynical, but this would be extremely hard to tes= t, and I don't feel up to the code review that would be required to provide sufficient confidence :-( NeilBrown >=20 > Cheers, >=20 > John. >=20 > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html --Sig_/lTqH2o=nDgbJ.0oFOs=Xr1x Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBUGuTEDnsnt1WYoG5AQKKyA//VC55S8fvT8m9UxRqzRV+L3GTxlBJlWBQ 3ib4DtinBk7DWY7qtT8RaPn53NCiehW9NtsecSVkC8sQdphLEBLmk13OdhRg3+OZ W6AOTMDf/x2+0eQZAbdIFfxMCCYcRvoRsiP9q5yds1uvWIE+xfXzrzorrdAfHzum uGAP1Xv25/Vnxez5etUVmkx51X4/n+vYwPFwROvkWgU8atWqesrnS0PazeXbYHsK lnvo7Q4n5VpJbfbAJF0O9SO53Lr4kReB2L5w4Nd3W4SPRDmlqn3sf6ezOjpOQpzk 1a32LLbR2EIgwPUdYoivqCuKemoOVspsiNi6dmUi5t6tlBGIUdoqOC5oc9nkqd2I q+++VA0RzFv4XYJ2EhoFMo5PQupeWGticgjSbnYl2+19O0/wDwXgncB8lQaTYWBz pfWjj8u6IvzTHPN/UD9/MPQ3rOr5uO+7IC2/ql+iwc8tGKz4B9klMhN5NBGEQe55 z0cssGVqiDxsKKIEohxbncxEHtbLYB/EqvmU9tNs1WiH0CC1HAN/5TAujrWTxjDC qwcVHeCFbDeW4r7/+pWAMNDrww6TOEwjzi3uRy3cl0RytDzJ4VLBLchiRtIipbJ+ vugK9vRfYl7yUeyl4tlSLJDrPU+fyvzHTtJD0yohxpBWRkSRiu0bmYY+34RTg5WE 1IbAznZYz4k= =CX8J -----END PGP SIGNATURE----- --Sig_/lTqH2o=nDgbJ.0oFOs=Xr1x--