From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from len.romanrm.net ([91.229.20.24]:39658 "EHLO len.romanrm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751693AbaANThH (ORCPT ); Tue, 14 Jan 2014 14:37:07 -0500 Date: Wed, 15 Jan 2014 01:37:03 +0600 From: Roman Mamedov To: Chris Murphy Cc: Btrfs BTRFS Subject: Re: How does btrfs handle bad blocks in raid1? Message-ID: <20140115013703.33bb2799@natsu> In-Reply-To: <486C0640-409D-4636-858C-84A679C0AF4E@colorremedies.com> References: <201401100106.s0A16CNd016476@atl4mhib27.myregisteredsite.com> <52CF4D5D.2010709@chinilu.com> <486C0640-409D-4636-858C-84A679C0AF4E@colorremedies.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/P6F/Wb.BPaJsOPLiL7pt.oQ"; protocol="application/pgp-signature" Sender: linux-btrfs-owner@vger.kernel.org List-ID: --Sig_/P6F/Wb.BPaJsOPLiL7pt.oQ Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 14 Jan 2014 12:13:09 -0700 Chris Murphy wrote: >=20 > On Jan 9, 2014, at 6:31 PM, George Mitchell wrote: > >>=20 > > Jim, my point was that IF the drive does not successfully resolve the b= ad block issue and btrfs takes a write failure every time it attempts to ov= erwrite the bad data, it is not going to remap that data, but rather it is = going to fail the drive. >=20 > If the drive doesn't resolve a bad block on write, then the drive is toas= t. I vaguely remember having some drives that were not able to remap a single block on write, but doing that successfully if I overwrote a sizable area around (and including) that block, or overwrite the whole drive. And after that they worked without issue not exhibiting further bad blocks. Or for example consider the 4k sector drives. If even any portion of the physical 4k sector is corrupt, some of the eight 512 virtual blocks will be unreadable; but the thing is, writing to ANY of them individually will fail, because the drive's internal r-m-w will fail to obtain all the pieces of the 4k sector from disk to overwrite it. So in my opinion one (and perhaps one of the easier) things to consider her= e, would be to try being "generous" in recovery-overwrite, say, rewrite a whole 1MB-sized region centered at the unreadable sector. --=20 With respect, Roman --Sig_/P6F/Wb.BPaJsOPLiL7pt.oQ Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlLVkd8ACgkQTLKSvz+PZwgSmQCeMLQhIxJySaLQUQ0Elya8qRJW NXwAn3CXk/wW1X4JF3kiMmPJMPlQLkcv =68R9 -----END PGP SIGNATURE----- --Sig_/P6F/Wb.BPaJsOPLiL7pt.oQ--