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,NICE_REPLY_A,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 2C85AC433E6 for ; Wed, 17 Feb 2021 18:04:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D630164E5B for ; Wed, 17 Feb 2021 18:04:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232953AbhBQSEn (ORCPT ); Wed, 17 Feb 2021 13:04:43 -0500 Received: from smtp.hosts.co.uk ([85.233.160.19]:45049 "EHLO smtp.hosts.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234782AbhBQSE2 (ORCPT ); Wed, 17 Feb 2021 13:04:28 -0500 Received: from host86-162-184-82.range86-162.btcentralplus.com ([86.162.184.82] helo=[192.168.1.65]) by smtp.hosts.co.uk with esmtpa (Exim) (envelope-from ) id 1lCRAt-0008Nr-BT; Wed, 17 Feb 2021 18:03:43 +0000 Subject: Re: use ssd as write-journal or lvm-cache? To: Peter Grandi , list Linux RAID References: <24620.56829.93946.65275@cyme.ty.sabi.co.uk> From: antlists Message-ID: <58ea0f6f-eb90-98e1-5f51-148fc0367843@youngman.org.uk> Date: Wed, 17 Feb 2021 18:03:45 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <24620.56829.93946.65275@cyme.ty.sabi.co.uk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On 17/02/2021 09:12, Peter Grandi wrote: >> I was to use ssd to cache my mdadm-raid5 + lvm storage. > Not that sure that layering MDADM on top of DM/LVM2 is always a > good idea, I tend to prefer to keep things simple. > Is that what the OP is doing? I don't think putting raid on top of lvm is a good idea, which is why I'm putting lvm on top of raid. Whatever, I guess you're better putting the cache on the bottom layer, just above the actual hardware. In my case, that would be caching the raid. Cheers, Wol