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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 6D403C4363A for ; Tue, 6 Oct 2020 03:11:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1704F206F4 for ; Tue, 6 Oct 2020 03:11:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725977AbgJFDLC (ORCPT ); Mon, 5 Oct 2020 23:11:02 -0400 Received: from james.kirk.hungrycats.org ([174.142.39.145]:47766 "EHLO james.kirk.hungrycats.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725909AbgJFDLC (ORCPT ); Mon, 5 Oct 2020 23:11:02 -0400 Received: by james.kirk.hungrycats.org (Postfix, from userid 1002) id 1010883E6B8; Mon, 5 Oct 2020 23:11:00 -0400 (EDT) Date: Mon, 5 Oct 2020 23:11:00 -0400 From: Zygo Blaxell To: Casey Matson-deKay Cc: linux-btrfs@vger.kernel.org Subject: Re: Best way to break RAID5/6? Message-ID: <20201006031100.GL5890@hungrycats.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Oct 05, 2020 at 06:46:53PM -0700, Casey Matson-deKay wrote: > Hi all, > > I'm new to the community, but love the work being done here. I'm an > embedded C developer and PCB designer, and would like to get involved > in btrfs. > > I, like many, am frustrated at the mystery of raid5/6 functionality. > More for the learning experience than anything, I was wondering about > the best known methods to break raid5/6 in a test setup, in order to > understand the patterns by which it breaks, and eventually, play > around with the kernel code to understand what's going on more in > depth. Welcome to btrfs! Here's a list of known raid5 bugs with background references: https://lore.kernel.org/linux-btrfs/20200627030614.GW10769@hungrycats.org/ > My initial thought, taking 3 USB drives, configuring them in RAID5, > and pulling one out during a write, seems a bit simplistic. Are there Just pulling one out is sufficient to hit the first bug: some reads fail in degraded mode. > known raid failure modes that would be more apt for learning and > understanding where the raid bugs lie in btrfs, and how to trigger and > explore them? > > Thank you! > > Casey