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 7B5B4C433EF for ; Mon, 13 Jun 2022 19:26:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348822AbiFMT0q (ORCPT ); Mon, 13 Jun 2022 15:26:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53286 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350372AbiFMT0K (ORCPT ); Mon, 13 Jun 2022 15:26:10 -0400 Received: from mail1.merlins.org (magic.merlins.org [209.81.13.136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 908CC213 for ; Mon, 13 Jun 2022 10:46:55 -0700 (PDT) Received: from rrcs-173-197-119-179.west.biz.rr.com ([173.197.119.179]:32409 helo=sauron.svh.merlins.org) by mail1.merlins.org with esmtpsa (Cipher TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94.2 #2) id 1o0nQp-0004HE-6g by authid with srv_auth_plain; Mon, 13 Jun 2022 10:46:42 -0700 Received: from merlin by sauron.svh.merlins.org with local (Exim 4.92) (envelope-from ) id 1o0o9A-00CBZl-L2; Mon, 13 Jun 2022 10:46:40 -0700 Date: Mon, 13 Jun 2022 10:46:40 -0700 From: Marc MERLIN To: Roman Mamedov Cc: Andrea Gelmini , Andrei Borzenkov , Zygo Blaxell , Josef Bacik , Chris Murphy , Qu Wenruo , "linux-btrfs@vger.kernel.org" Subject: Re: Suggestions for building new 44TB Raid5 array Message-ID: <20220613174640.GL1664812@merlins.org> References: <20220611145259.GF1664812@merlins.org> <20220613022107.6eafbc1c@nvm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220613022107.6eafbc1c@nvm> X-Sysadmin: BOFH X-URL: http://marc.merlins.org/ X-SA-Exim-Connect-IP: 173.197.119.179 X-SA-Exim-Mail-From: marc@merlins.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Jun 13, 2022 at 02:21:07AM +0500, Roman Mamedov wrote: > On Sat, 11 Jun 2022 07:52:59 -0700 > Marc MERLIN wrote: > > > On Sat, Jun 11, 2022 at 02:30:33PM +0500, Roman Mamedov wrote: > > > > 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? > > > > Hard to know either way, trading one layer for another, and LVM has > > always seemed heavier > > I'd suggest to put the LUKS volume onto an LV still (in case you don't), so you > can add and remove cache just to see how it works; unlike with bcache, an LVM > cache can be added to an existing LV and then removed without a trace, all > without having to displace 44 TB of data for that. Thanks. I've always felt that LVM was heavyweight and required extra steps and tools, so I've been avoiding it, but maybe that wasn't rational. bcache by the way, you can set it up without a backing device and then use it normally without the cache layer. I think it's actually pretty similar, but you have to set it up beforehand (just like LVM) Marc -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Home page: http://marc.merlins.org/ | PGP 7F55D5F27AAF9D08