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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 2BFCBC433DF for ; Fri, 19 Jun 2020 07:51:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0A55F207FC for ; Fri, 19 Jun 2020 07:51:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730828AbgFSHvb (ORCPT ); Fri, 19 Jun 2020 03:51:31 -0400 Received: from len.romanrm.net ([91.121.86.59]:34768 "EHLO len.romanrm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730599AbgFSHvb (ORCPT ); Fri, 19 Jun 2020 03:51:31 -0400 X-Greylist: delayed 384 seconds by postgrey-1.27 at vger.kernel.org; Fri, 19 Jun 2020 03:51:30 EDT Received: from natsu (unknown [IPv6:fd39::e99e:8f1b:cfc9:ccb8]) by len.romanrm.net (Postfix) with SMTP id 0FE9B4009F; Fri, 19 Jun 2020 07:45:04 +0000 (UTC) Date: Fri, 19 Jun 2020 12:45:05 +0500 From: Roman Mamedov To: Daniel Smedegaard Buus Cc: linux-btrfs@vger.kernel.org Subject: Re: Behavior after encountering bad block Message-ID: <20200619124505.586f2b63@natsu> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, 19 Jun 2020 09:24:26 +0200 Daniel Smedegaard Buus wrote: > I was testing btrfs to see data checksumming behavior when > encountering a rotten area, so I set up a loop device backed by a 1GB > file. I filled it with a compressed file and made it rot with, e.g., > > dd if=/dev/zero of=loopie bs=1k seek=800000 count=1 > > That is, the equivalent of having data on a single block on an actual > hard drive go bad. Not really, because when real on-disk sectors go bad, the (properly behaving) drive will return I/O errors, not blocks of zeroes instead. For a closer emulation of hardware bad sectors, check out dm-dust: https://www.kernel.org/doc/html/latest/admin-guide/device-mapper/dm-dust.html Roman