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 97215C433DB for ; Tue, 5 Jan 2021 06:39:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5739F207B2 for ; Tue, 5 Jan 2021 06:39:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726497AbhAEGjr convert rfc822-to-8bit (ORCPT ); Tue, 5 Jan 2021 01:39:47 -0500 Received: from mail.eclipso.de ([217.69.254.104]:52336 "EHLO mail.eclipso.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725290AbhAEGjr (ORCPT ); Tue, 5 Jan 2021 01:39:47 -0500 Received: from mail.eclipso.de (www1.eclipso.de [217.69.254.102]) by mail.eclipso.de with ESMTP id 26EF1C14 for ; Tue, 05 Jan 2021 07:39:05 +0100 (CET) Date: Tue, 05 Jan 2021 07:39:05 +0100 MIME-Version: 1.0 Message-ID: <28232f6c03d8ae635d2ddffe29c82fac@mail.eclipso.de> X-Mailer: eclipso / 7.4.0 From: " " Subject: Raid1 of a slow hdd and a fast(er) SSD, howto to prioritize the SSD? Reply-To: " " To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org ­I have put a SSD and a slow laptop HDD in btrfs raid. This was a bad idea, my system does not feel responsive. When i load a program, dstat shows half of the program is loaded from the SSD, and the rest from the slow hard drive. I was expecting btrfs to do almost all reads from the fast SSD, as both the data and the metadata is on that drive, so the slow hdd is only really needed when there's a bitflip on the SSD, and the data has to be reconstructed. Writing has to be done to both drives of course, but I don't expect slowdowns from that, as the system RAM should cache that. Is there a way to tell btrfs to leave the slow hdd alone, and to prioritize the SSD? In detail: # mkfs.btrfs -f -d raid1 -m raid1 /dev/sda1 /dev/sdb1 # btrfs filesystem show / Label: none uuid: 485952f9-0cfc-499a-b5c2-xxxxxxxxx Total devices 2 FS bytes used 63.62GiB devid 2 size 223.57GiB used 65.03GiB path /dev/sda1 devid 3 size 149.05GiB used 65.03GiB path /dev/sdb1 $ dstat -tdD sda,sdb --nocolor ----system---- --dsk/sda-- --dsk/sdb-- time | read writ: read writ 05-01 08:19:39| 0 0 : 0 0 05-01 08:19:40| 0 4372k: 0 4096k 05-01 08:19:41| 61M 4404k: 16k 4680k 05-01 08:19:42| 52M 0 :6904k 0 05-01 08:19:43|4556k 76k: 31M 76k 05-01 08:19:44|2640k 0 : 38M 0 05-01 08:19:45|4064k 0 : 30M 0 05-01 08:19:46|1252k 0 : 30M 0 05-01 08:19:47|2572k 0 : 37M 0 05-01 08:19:48|5840k 0 : 27M 0 05-01 08:19:49|4480k 492k: 22M 492k 05-01 08:19:50|1284k 0 : 44M 0 05-01 08:19:51|1184k 0 : 33M 0 05-01 08:19:52|3592k 0 : 31M 0 05-01 08:19:53| 14M 156k:8268k 156k 05-01 08:19:54| 22M 1956k: 0 1956k 05-01 08:19:55| 0 0 : 0 0 05-01 08:19:56|7636k 0 : 0 0 05-01 08:19:57| 23M 116k: 0 116k 05-01 08:19:58|2296k 552k: 0 552k 05-01 08:19:59| 624k 132k: 0 132k 05-01 08:20:00| 0 0 : 0 0 05-01 08:20:01|6948k 188k: 0 188k 05-01 08:20:02| 0 1340k:4364k 1340k 05-01 08:20:03| 0 0 : 0 0 05-01 08:20:04| 0 484k: 0 484k 05-01 08:20:05| 0 0 : 0 0 05-01 08:20:06| 0 0 : 0 0 05-01 08:20:07| 0 0 : 0 0 05-01 08:20:08| 0 84k: 0 84k 05-01 08:20:09| 0 132k: 0 132k 05-01 08:20:10| 0 0 : 0 0 05-01 08:20:11| 0 7616k: 96k 7584k 05-01 08:20:12| 0 2264k: 0 2296k 05-01 08:20:13| 0 0 : 0 0 05-01 08:20:14| 0 1956k: 0 1956k 05-01 08:20:15| 0 0 : 0 0 05-01 08:20:16| 0 0 : 0 0 # fdisk -l **This is the SSD** Disk /dev/sda: 223.57 GiB, 240057409536 bytes, 468862128 sectors Disk model: CT240BX200SSD1 Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disklabel type: dos Disk identifier: 0x12cfb9e1 Device Boot Start End Sectors Size Id Type /dev/sda1 2048 468862127 468860080 223.6G 83 Linux **This is the hard drive** Disk /dev/sdb: 149.05 GiB, 160041885696 bytes, 312581808 sectors Disk model: Hitachi HTS54321 Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0x20000000 Device Boot Start End Sectors Size Id Type /dev/sdb1 2048 312581807 312579760 149G 83 Linux --- Take your mailboxes with you. Free, fast and secure Mail & Cloud: https://www.eclipso.eu - Time to change!