From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C434BC282CE for ; Wed, 22 May 2019 19:00:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A2CE520645 for ; Wed, 22 May 2019 19:00:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729528AbfEVTAT (ORCPT ); Wed, 22 May 2019 15:00:19 -0400 Received: from frost.carfax.org.uk ([85.119.82.111]:58732 "EHLO frost.carfax.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728533AbfEVTAT (ORCPT ); Wed, 22 May 2019 15:00:19 -0400 Received: from hrm by frost.carfax.org.uk with local (Exim 4.80) (envelope-from ) id 1hTWTJ-000676-0A; Wed, 22 May 2019 19:00:17 +0000 Date: Wed, 22 May 2019 19:00:16 +0000 From: Hugo Mills To: Cerem Cem ASLAN Cc: Btrfs BTRFS Subject: Re: Citation Needed: BTRFS Failure Resistance Message-ID: <20190522190016.GA9329@carfax.org.uk> Mail-Followup-To: Hugo Mills , Cerem Cem ASLAN , Btrfs BTRFS References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="Q68bSM7Ycu6FN28Q" Content-Disposition: inline In-Reply-To: X-GPG-Fingerprint: DD84 D558 9D81 DDEE 930D 2054 585E 1475 E2AB 1DE4 X-GPG-Key: E2AB1DE4 X-Parrot: It is no more. It has joined the choir invisible. X-IRC-Nicks: darksatanic darkersatanic darkling darkthing User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org --Q68bSM7Ycu6FN28Q Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, May 22, 2019 at 09:46:42PM +0300, Cerem Cem ASLAN wrote: > Could you confirm or disclaim the following explanation: > https://unix.stackexchange.com/a/520063/65781 Well, the quoted comment at the top is accurate (although I haven't looked for the IRC conversation in question). However, there are some inaccuracies in the detailed comment below. These aren't particularly relevant to the argument addressing your question, but do detract somewhat from the authority of the answer. :) Specifically: Btrfs doesn't use Merkle trees. It uses CoW-friendly B-trees -- there's no csum of tree contents. It also doesn't make a complete copy of the tree (that would take a long time). Instead, it'll only update the blocks in the tree that need updating, which will bubble the changes up through the tree node path to the top level. There's a detailed description of the issues of broken hardware on the btrfs wiki, here: https://btrfs.wiki.kernel.org/index.php/FAQ#What_does_.22parent_transid_verify_failed.22_mean.3F Hugo. -- Hugo Mills | Why play all the notes, when you need only play the hugo@... carfax.org.uk | most beautiful? http://carfax.org.uk/ | PGP: E2AB1DE4 | Miles Davis --Q68bSM7Ycu6FN28Q Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJc5ZxAAAoJEFheFHXiqx3k+e0QALoGO8YfeeMOvKceACTIM5fo Su1nEBPgPVi++7a4RXTryuJaJ7rbVF9T4Bs4mz9nhwN7Nu4adw2wxRCienn9jcH3 TxWiu44kyIMvajYl88DToIHja8GotcWJj8s7xX3+LNilB2ERyIshsaF5YZDa6hkT V5ODqSYaZ3pxbpISeA+1IrEZcVryvSEuH+mbpeKfcm1iWnuG/vcyuSqoC0wjg9lC FmkTucSURWSw8nUrbHRhkhQc6bahWI9KizXlGvJzrVHYdAlnpgWbZkTw/t4cpp69 TkGiO2O7r/PrQ7pd6QWckIguF0CWm/GuQ/IeFjDR8xLtb9VIsP50+kYJi14caNLA kNg2xUfEwsZT/mEJCrnAqytiftIAwzUDi/COIVlyTlrpEcfWm/1beknstWbQwImu Zh/p2vXRmAPOXkgYvDeAM3HnJs9RttWqzuZXcsFtz1p4rAxPgTNRCuPhiFxO+1Xm 8Lon3uTCiG5kLJ6ylV68XmAaQpSpvOVQvshjRjIH/g9zHZIFBoevzqVYsDq/RqS5 +A3ugR+4ha6HOrMhKqioer0Q33m4aRy5tHT+fxyDIZUJohvxTJ6ZlJlNe9FvjXlY Sf95GpgbSzW5sQ2jxpNDnKHIgkogChFtVW2Qt53YHro0gL2FRyzA3MxjjB0lmeja v2/p4Dkkdqs5GjelZRPM =OflW -----END PGP SIGNATURE----- --Q68bSM7Ycu6FN28Q--