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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 076F4C433E6 for ; Sat, 29 Aug 2020 15:57:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DC49A20707 for ; Sat, 29 Aug 2020 15:57:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728402AbgH2P5u (ORCPT ); Sat, 29 Aug 2020 11:57:50 -0400 Received: from rin.romanrm.net ([51.158.148.128]:56286 "EHLO rin.romanrm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728300AbgH2P5j (ORCPT ); Sat, 29 Aug 2020 11:57:39 -0400 Received: from natsu (unknown [IPv6:fd39::e99e:8f1b:cfc9:ccb8]) by rin.romanrm.net (Postfix) with SMTP id CB932410; Sat, 29 Aug 2020 15:57:35 +0000 (UTC) Date: Sat, 29 Aug 2020 20:57:35 +0500 From: Roman Mamedov To: antlists Cc: Ram Ramesh , "R. Ramesh" , Linux Raid Subject: Re: Best way to add caching to a new raid setup. Message-ID: <20200829205735.58dfcda1@natsu> In-Reply-To: <6a9fc5ae-1cae-a3d6-6dc3-d1a93dc1e38e@youngman.org.uk> References: <16cee7f2-38d9-13c8-4342-4562be68930b.ref@verizon.net> <16cee7f2-38d9-13c8-4342-4562be68930b@verizon.net> <20200828224616.58a1ad6c@natsu> <448afb39-d277-445f-cc42-2dfc5210da7b@gmail.com> <6a9fc5ae-1cae-a3d6-6dc3-d1a93dc1e38e@youngman.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-raid-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On Sat, 29 Aug 2020 16:34:56 +0100 antlists wrote: > On 28/08/2020 21:39, Ram Ramesh wrote: > > One thing about LVM that I am not clear. Given the choice between > > creating /mirror LV /on a VG over simple PVs and /simple LV/ over raid1 > > PVs, which is preferred method? Why? > > Simplicity says have ONE raid, with ONE PV on top of it. > > The other way round is you need TWO SEPARATE (at least) PV/VG/LVs, which > you then stick a raid on top. I believe the question was not about the order of layers, but whether to create a RAID with mdadm and then LVM on top, vs. abandoning mdadm and using LVM's built-in RAID support instead: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/logical_volume_manager_administration/mirror_create Personally I hugely prefer mdadm, due to the familiar and convenient interface of the program itself, as well as of /proc/mdstat. -- With respect, Roman