From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f195.google.com ([209.85.223.195]:33275 "EHLO mail-io0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752202AbdDDNwT (ORCPT ); Tue, 4 Apr 2017 09:52:19 -0400 Received: by mail-io0-f195.google.com with SMTP id f84so15090060ioj.0 for ; Tue, 04 Apr 2017 06:52:18 -0700 (PDT) Subject: Re: Need some help: "BTRFS critical (device sda): corrupt leaf, slot offset bad: block" To: Brian B , Robert Krig , Hans van Kranenburg , linux-btrfs@vger.kernel.org References: <635a5ca8-9fa5-6cd4-21b5-97f9f3db93d3@render-wahnsinn.de> <98a478cf-20f9-981f-6da5-4186a10be303@render-wahnsinn.de> <7f94b6b9-f18d-14dd-4a20-1793ce08df8a@render-wahnsinn.de> <36448783-672c-5e88-cdda-9a8679c4b4ad@render-wahnsinn.de> <0eda9836-a4ee-b666-2a05-b4bb26746b1a@sd85.net> From: "Austin S. Hemmelgarn" Message-ID: Date: Tue, 4 Apr 2017 09:52:12 -0400 MIME-Version: 1.0 In-Reply-To: <0eda9836-a4ee-b666-2a05-b4bb26746b1a@sd85.net> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2017-04-04 09:29, Brian B wrote: > On 04/04/2017 12:02 AM, Robert Krig wrote: >> My storage array is BTRFS Raid1 with 4x8TB Drives. >> Wouldn't it be possible to simply disconnect two of those drives, mount >> with -o degraded and still have access (even if read-only) to all my data? > Just jumping on this point: my understanding of BTRFS "RAID1" is that > each file (block?) is randomly assigned to two disks of the array (no > matter how many disks are in the array). So if you remove two disks, > you will probably have files that were "assigned" to both of those > disks, and will be missing. > > In short, you can't remove more than one disk of a BTRFS RAID1 and still > have all of your data. > That understanding is correct. From a functional perspective, BTRFS raid1 is currently a RAID10 implementation with striping happening at a very large granularity.