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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F700C433EF for ; Sat, 11 Jun 2022 09:30:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230234AbiFKJar (ORCPT ); Sat, 11 Jun 2022 05:30:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34474 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231571AbiFKJao (ORCPT ); Sat, 11 Jun 2022 05:30:44 -0400 Received: from rin.romanrm.net (rin.romanrm.net [IPv6:2001:bc8:2dd2:1000::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF96E3152C for ; Sat, 11 Jun 2022 02:30:38 -0700 (PDT) Received: from nvm (nvm2.home.romanrm.net [IPv6:fd39::4a:3cff:fe57:d6b5]) by rin.romanrm.net (Postfix) with SMTP id AFF7C46; Sat, 11 Jun 2022 09:30:34 +0000 (UTC) Date: Sat, 11 Jun 2022 14:30:33 +0500 From: Roman Mamedov To: Marc MERLIN Cc: Andrei Borzenkov , Zygo Blaxell , Josef Bacik , "linux-btrfs@vger.kernel.org" , Chris Murphy , Qu Wenruo Subject: Re: Suggestions for building new 44TB Raid5 array Message-ID: <20220611143033.56ffa6af@nvm> In-Reply-To: <20220611045120.GN22722@merlins.org> References: <20220611045120.GN22722@merlins.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, 10 Jun 2022 21:51:20 -0700 Marc MERLIN wrote: > Kernel will be 5.16. Filesystem will be 24TB and contain mostly bigger > files (100MB to 10GB). > 2) echo 0fb96f02-d8da-45ce-aba7-070a1a8420e3 > /sys/block/bcache64/bcache/attach > gargamel:/dev# cat /sys/block/md7/bcache/cache_mode > [writethrough] writeback writearound none Maybe try LVM Cache this time? > 3) cryptsetup luksFormat --align-payload=2048 -s 256 -c aes-xts-plain64 /dev/bcache64 > 4) cryptsetup luksOpen /dev/bcache64 dshelf1 What's the threat scenario for LUKS on the array? A major one for me would be not to be having to RMA a disk with all my data still on the platters. But with RAID5, a single disk by itself would not contain easily discernible or usable data. Or if you're protecting against unauthorized access to the entire array, then never mind. > 5) mkfs.btrfs -m dup -L dshelf1 /dev/mapper/dshelf1 Personally I have switched from Btrfs on MD to individual disks and MergerFS. The rationale for no RAID is the simplicity and resilience of the individual single-disk filesystems, and that anything important or not easily re-obtainable is backed up anyways; so the protection from single disk failures is not as important, compared to the introduced complexity and the chance of losing the entire huge FS (like you had). -- With respect, Roman