From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from len.romanrm.net ([91.229.20.24]:44646 "EHLO len.romanrm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751761AbaANVy2 (ORCPT ); Tue, 14 Jan 2014 16:54:28 -0500 Date: Wed, 15 Jan 2014 03:54:25 +0600 From: Roman Mamedov To: Chris Murphy Cc: Btrfs BTRFS Subject: Re: How does btrfs handle bad blocks in raid1? Message-ID: <20140115035425.7395087f@natsu> In-Reply-To: <6F3D91C0-8CCA-4713-BFEC-244E3D65F306@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> <20140115031927.4fd1d44b@natsu> <6F3D91C0-8CCA-4713-BFEC-244E3D65F306@colorremedies.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/5t2GEVfWBwpdA4hP9K+rQY3"; protocol="application/pgp-signature" Sender: linux-btrfs-owner@vger.kernel.org List-ID: --Sig_/5t2GEVfWBwpdA4hP9K+rQY3 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 14 Jan 2014 14:37:46 -0700 Chris Murphy wrote: > Reserve sectors are fundamental to ECC. If there are no more reserves, the > status should be a failed drive, it can no longer do its own relocation of > data experiencing transient read errors in this case. With the Reallocated sector count being low in that case, I assume the drive *had* a lot of reserve space, but due to a buggy firmware didn't "see the n= eed to use it" just yet for this particular sector. It's not the question of what is "fundamental" or right, I am describing observed behavior in the real world - and yes, of course, that behavior is incorrect and probably an indication of a buggy peculiar firmware. > I'm considering persistent write failure as a result of no more reserve > sectors being available. Write doesn't fail, it succeeds, but you still can't read back the bad bloc= k. And the "reallocated sector count" does not increase. > Well, not totally useless, if it flags the user with an hour's notice in = Gnome, If we're again talking the user GUI-level indicators, then an increase in "Reallocated sector count", "Current pending sectors" or "Reported uncorrectable" should also be a reason for such GUI notice to appear. And AFAIK that's how smartd howto/manual recommends configuring it (i.e. an E-M= ail on any change in those critical attributes). > >> a way to send a command to the firmware to persistently increase the r= eserve > >> 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. > >=20 > > Yes please that, and also a pony. :) >=20 > That seems a lot easier to implement than anything else being discussed.= =20 Oh really? Pushing that feature into multiple competing vendor's HDD firmwa= res across diverse models, product lines, interfaces and revisions is *easier* = than mainlining a patch into the Linux kernel?... My point was that this would h= ave been a good feature, but no chance we're going to see it realized. --=20 With respect, Roman --Sig_/5t2GEVfWBwpdA4hP9K+rQY3 Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlLVshIACgkQTLKSvz+PZwhtWwCfeF+LhRob6hGBAYsrsA/EUNNg yCQAnir/dHYUSKu7/7SXbDse6Gsk+/1i =dCs8 -----END PGP SIGNATURE----- --Sig_/5t2GEVfWBwpdA4hP9K+rQY3--