From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from len.romanrm.net ([91.229.20.24]:36129 "EHLO len.romanrm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751580AbaANVTa (ORCPT ); Tue, 14 Jan 2014 16:19:30 -0500 Date: Wed, 15 Jan 2014 03:19:27 +0600 From: Roman Mamedov To: Chris Murphy Cc: Btrfs BTRFS Subject: Re: How does btrfs handle bad blocks in raid1? Message-ID: <20140115031927.4fd1d44b@natsu> In-Reply-To: <1207CF09-B2A4-4DB6-9CA8-C3C78C1DA0F3@colorremedies.com> References: <201401100106.s0A16CNd016476@atl4mhib27.myregisteredsite.com> <52CF4D5D.2010709@chinilu.com> <486C0640-409D-4636-858C-84A679C0AF4E@colorremedies.com> <20140115013703.33bb2799@natsu> <1207CF09-B2A4-4DB6-9CA8-C3C78C1DA0F3@colorremedies.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/1Hj/+SU_.qg5FpbzA8MElJ9"; protocol="application/pgp-signature" Sender: linux-btrfs-owner@vger.kernel.org List-ID: --Sig_/1Hj/+SU_.qg5FpbzA8MElJ9 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 14 Jan 2014 14:05:11 -0700 Chris Murphy wrote: >=20 > On Jan 14, 2014, at 12:37 PM, Roman Mamedov wrote: > >=20 > > I vaguely remember having some drives that were not able to remap a sin= gle > > block on write, but doing that successfully if I overwrote a sizable ar= ea > > around (and including) that block, or overwrite the whole drive. And af= ter > > that they worked without issue not exhibiting further bad blocks. >=20 > Presumably the SMART self-assessment for this drive was FAIL?=20 No of course not, why? SMART goes to FAIL only if one of the attributes fal= ls below threshold, in this case that would be Reallocated Sector Count having too much sectors. But nope, it either had zero, or in single-digit numbers. I don't ever remember seeing a SMART FAIL drive that would function in any usual sense of that word. Whereas such pecularities (bad sectors / unremappable sectors / not wanting to remap until you overwrite large area = and perhaps even multiple times at that), all with SMART =3D PASS, are seen left right and center. > And if so what's the point of the work around when we only have a pass/fa= il > level granularity for drive health? Not sure what you're referring to here. As said above, the FAIL/PASS status= is largely useless, and the more important indicators are the values and dynam= ics in Reallocated sector count, Current pending sectors, Reported uncorrectabl= e, etc. > a way to send a command to the firmware to persistently increase the rese= rve > sectors at the expensive of available space - in effect it reduces the LBA > count by e.g. 10MB, thereby increasing the reserve pool by 10MB. Yes please that, and also a pony. :) -=20 With respect, Roman --Sig_/1Hj/+SU_.qg5FpbzA8MElJ9 Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlLVqd8ACgkQTLKSvz+PZwhBaACgkMGzdB32ZvgkriTQSLa6sdKS 9ogAnjKVz8wO1Kc1D24ZuL1Ow3d3Tavw =1Mg6 -----END PGP SIGNATURE----- --Sig_/1Hj/+SU_.qg5FpbzA8MElJ9--