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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 A0F99C433E9 for ; Thu, 4 Feb 2021 17:44:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5DEB264F4D for ; Thu, 4 Feb 2021 17:44:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238575AbhBDRo0 convert rfc822-to-8bit (ORCPT ); Thu, 4 Feb 2021 12:44:26 -0500 Received: from mail.eclipso.de ([217.69.254.104]:39386 "EHLO mail.eclipso.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238582AbhBDRoR (ORCPT ); Thu, 4 Feb 2021 12:44:17 -0500 Received: from mail.eclipso.de (www1.eclipso.de [217.69.254.102]) by mail.eclipso.de with ESMTP id 6F4CC1F7 for ; Thu, 04 Feb 2021 18:43:23 +0100 (CET) Date: Thu, 04 Feb 2021 18:43:23 +0100 MIME-Version: 1.0 Message-ID: <24e578627d205151df16b5aebe4a551e@mail.eclipso.de> X-Mailer: eclipso / 7.4.0 From: " " Subject: Re: Re: put 2 hard drives in mdadm raid 1 and detect bitrot like btrfs does, what's that called? Reply-To: " " To: "Andy Smith" Cc: , In-Reply-To: <20210204105457.GI3712@bitfolk.com> References: <20210204105457.GI3712@bitfolk.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org --- Ursprüngliche Nachricht --- Von: Andy Smith Datum: 04.02.2021 11:54:57 An: linux-btrfs@vger.kernel.org Betreff: Re: put 2 hard drives in mdadm raid 1 and detect bitrot like btrfs does, what's that called? Hi Cedric, On Wed, Feb 03, 2021 at 08:33:18PM +0100, wrote: > it's called "dm-integrity", as mentioned in this e-mail: > https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg93037.html If you do this it would be very interesting to see performance figures for the following setups: - btrfs with raid1 meta and data allocation - mdadm raid1 on raw devices - mdadm raid1 on dm-integrity (no encryption) on raw devices - mdadm raid1 on dm-integrity (encryption) on raw devices just to see what kind of performance loss dm-integrity and encryption is going to impose. After doing it, it would find a nice home on the Linux RAID wiki: https://raid.wiki.kernel.org/index.php/Dm-integrity Cheers, Andy Hey Andy, I would rather see performance figures for these setups: A) btrfs with 2 (or more) hard drives and one SSD in writeback bcache configuration (unsafe against failure of the ssd): +-----------------------------+ | btrfs raid 1 /mnt | +--------------+--------------+ | /dev/Bcache0 | /dev/Bcache1 | +--------------+--------------+ | bcache writeback Cache | | /dev/sdk1 | +--------------+--------------+ | Data | Data | | /dev/sdv1 | /dev/sdw1 | +--------------+--------------+ B) btrfs with 2 (or more) hard drives and two SSD's in dm-raid 1 writeback bcache configuration (unsafe against corruption of any of the ssd's): +-----------------------------+ | btrfs raid 1 /mnt | +--------------+--------------+ | /dev/Bcache0 | /dev/Bcache1 | +--------------+--------------+ | bcache writeback Cache | | /dev/dm0 | +--------------+--------------+ | 2x SSD in mdadm raid 1 | | /dev/sdk1 /dev/sdl1 | +--------------+--------------+ | Data | Data | | /dev/sdv1 | /dev/sdw1 | +--------------+--------------+ C) Full stack: btrfs with 2 (or more) hard drives and two identical SSD's in dm-raid 1 with dm-integrity writeback bcache configuration (safe against any failed drive): +-----------------------------+ | btrfs raid 1 /mnt | +--------------+--------------+ | /dev/Bcache0 | /dev/Bcache1 | +--------------+--------------+ | bcache writeback Cache | | /dev/dm0 | +--------------+--------------+ | 2 x dm-integrity devices | | in mdadm raid 1 | +--------------+--------------+ | SSD hosting | SSD hosting | | dm-integrity | dm-integrity | | /dev/sdk1 | /dev/sdl1 | +--------------+--------------+ | Data | Data | | /dev/sdv1 | /dev/sdw1 | +--------------+--------------+ D) Full stack: btrfs with 2 (or more) hard drives and two SSD's (one slow, and one very fast) in dm-raid 1 with dm-integrity writeback bcache configuration (safe against any failed drive): +-----------------------------+ | btrfs raid 1 /mnt | +--------------+--------------+ | /dev/Bcache0 | /dev/Bcache1 | +--------------+--------------+ | bcache writeback Cache | | /dev/dm0 | +--------------+--------------+ | 2 x dm-integrity devices | | in mdadm raid 1 | +--------------+--------------+ | SSD hosting | SSD hosting | | dm-integrity | dm-integrity | | /dev/sdk1 | /dev/sdl1 | +--------------+--------------+ | Data | Data | | /dev/sdv1 | /dev/sdw1 | +--------------+--------------+ In all these setups, the performance of the hard drives is irrelevant, because the speed of the setups comes from the bcache SSD. Cheers, Cedric --- Take your mailboxes with you. Free, fast and secure Mail & Cloud: https://www.eclipso.eu - Time to change!