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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 B1452C433ED for ; Fri, 21 May 2021 12:06:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 970EE61090 for ; Fri, 21 May 2021 12:06:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229655AbhEUMHz (ORCPT ); Fri, 21 May 2021 08:07:55 -0400 Received: from correo01.aragon.es ([188.244.81.25]:17164 "EHLO aragon.es" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229507AbhEUMHy (ORCPT ); Fri, 21 May 2021 08:07:54 -0400 X-Greylist: delayed 605 seconds by postgrey-1.27 at vger.kernel.org; Fri, 21 May 2021 08:07:53 EDT Received: from aragon.es ([172.30.3.33]) by FM3.aragon.es with ESMTP id 14LBuHLm031712-14LBuHLn031712 for ; Fri, 21 May 2021 13:56:17 +0200 Received: from [1.8.2.59] (account scastillo@aragon.es [1.8.2.59] verified) by aragon.es (CommuniGate Pro SMTP 6.2.12) with ESMTPSA id 91114546 for linux-bcache@vger.kernel.org; Fri, 21 May 2021 13:56:17 +0200 To: linux-bcache@vger.kernel.org From: Santiago Castillo Oli Subject: Best strategy for caching VMs storage Message-ID: <08e95aaf-a5e5-fb32-31ea-ca35cc028fac@aragon.es> Date: Fri, 21 May 2021 13:56:16 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: es-ES X-FE-Policy-ID: 21:5:5:aragon.es Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org Hi there. I have a host running 4 VMs using qcow2 storage on a ext4 fs over HDD. Each VM has 3 qcow files (system, data and swap). I know I have an I/O bottleneck. I want to use bcache with an SSD to accelerate disk access but I´m not sure where should I put bcache on storage stack. Should I use bcache on host or in guests? Just one bcache backing device for a single (ext4) filesystem with all qcow files there, or different bcache and backing devices for each qcow2 file? Right know, I prefer qcow2 over thin-lvm for storage, but i could change my mind if thin-lvm is a much better combination for bcache. What would be the best strategy for caching VMs storage ? Any recommendation, please? Regards and thank you -- ___________________________________________________________