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 B2CAEC433FE for ; Fri, 21 Oct 2022 11:51:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229823AbiJULv4 (ORCPT ); Fri, 21 Oct 2022 07:51:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40340 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229568AbiJULvz (ORCPT ); Fri, 21 Oct 2022 07:51:55 -0400 Received: from mail-ua1-x92c.google.com (mail-ua1-x92c.google.com [IPv6:2607:f8b0:4864:20::92c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D13924B337 for ; Fri, 21 Oct 2022 04:51:54 -0700 (PDT) Received: by mail-ua1-x92c.google.com with SMTP id i16so2251460uak.1 for ; Fri, 21 Oct 2022 04:51:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=6kWyDVwGOCOJvN9GWcgaDEQaOVNt1oKvYS0iumVm3ek=; b=GReKr6sa9BNdXUL2rfV3KHZucbK+ZeowOQIvbKK0JvCSqEdM5ufOMcmxE85g0t7Blr 3lXfN0aqTbOMBzCHvCqDPVTs+p0r4dsd7sSWdJ+Jt/UbJiRxlkVBmyYTV6VqXT7f6foi 2siGcvT7AhJey2vgf2QDTnfEeGsa9n6+rpGm9DH6d9zkdoLEPto5CpzjUkI5jaS3QMUK XMzsnOjWvjgyQRe8RAZHhur90RSsTFjCQm6V38xGpA08PLea7/phZdYszUxCdKsJqKUB sioxZ0034Iv5VzvtQ8KH/Kepz3xSfJwbzHkl/Eek+XI00mw9Jx3KpvvAp3C6X437lBBC tJ1A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=6kWyDVwGOCOJvN9GWcgaDEQaOVNt1oKvYS0iumVm3ek=; b=Oos3BGNel2jWrBzjU7b2m2h+PIRUYxkl7px6l6STjWb/4TdZ/z5MZvWRx+guTnlfwf wAVDl26KLbsCahAH7MPnVsWo6DlcXDw0yBP++fecHciQSsbWkUJKGxTkA5OFq5ILed+g h2rrMW/oD6mQvDE+2rkKjKHV5cta/FxVzUwGbVYtLhc1eYE6FLLtuq1WX0bE6MoASbhT 0FbIAfEkFLx7CFkwOb/WX5R5EYnRwWkET96Bi8GXqgcyNkHp4Tei+/ZttjpsHdPQNxDg gItRn4SB5QxiqoRu/cgDTxIGorS6XVmp/1WqZJmRovCdWIOgKaKQONF5KMEXaUOx3i4d KmPw== X-Gm-Message-State: ACrzQf0sL5EA0BMDXCetwrZHj9jVJujhDmnxtUb3rvan6bc/KRqhxmQx o1qfs6iL+dp3JyuhwjxYN1j8Rr7uoNR1wQm5WFRoR8ko X-Google-Smtp-Source: AMsMyM6hyo+9TCdAuQFWDSLyAqHq7bRvit6aMhrJ1P+4ujZT5pLJrNsC/Git3mX5jZGnWWgth3Ww2C//dJhOiTf5PH8= X-Received: by 2002:ab0:25d4:0:b0:3c1:c353:31cb with SMTP id y20-20020ab025d4000000b003c1c35331cbmr12548896uan.63.1666353112720; Fri, 21 Oct 2022 04:51:52 -0700 (PDT) MIME-Version: 1.0 References: <7ca2b272-4920-076f-ecaf-5109db0aae46@youngman.org.uk> <20221021001405.2uapizqtsj3wxptb@bitfolk.com> <6c31fc94-b70e-88c5-205a-efff32baf594@plouf.fr.eu.org> <20221021105107.nhihftkjck74jg6i@bitfolk.com> In-Reply-To: <20221021105107.nhihftkjck74jg6i@bitfolk.com> From: Roger Heflin Date: Fri, 21 Oct 2022 06:51:41 -0500 Message-ID: Subject: Re: Performance Testing MD-RAID10 with 1 failed drive To: linux-raid@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org It is likely much simpler. Using a 2 disks raid 1 array with 100 reads iops and 100 write iops to the filesystem you would see this with 2 disks: 150 iops per disk (100 writes + 50 reads), but with one disk only in the raid you see 200 iops/disk (100 reads+100writes) and at that 7200 rpm spinning disks would be overcapacity. Now with 8 disks the numbers scale up, but the general idea is still the same. Once a disk fails then all of the reads it was handling have to go to the single remaining disk and that read load could result in that remaining disk not being able to keep up. The original poster needs to get sar or iostat stat to see what the actual io rates are, but if they don't understand what the spinning disk array can do fully redundant and with a disk failed it is not unlikely that the IO load is higher than a can be sustained with a single disk failed. On Fri, Oct 21, 2022 at 6:34 AM Andy Smith wrote: > > Hello, > > On Fri, Oct 21, 2022 at 10:15:42AM +0200, Pascal Hambourg wrote: > > Le 21/10/2022 =C3=A0 02:14, Andy Smith a =C3=A9crit : > > > Perhaps you could use dm-dust to make an unreliable block device > > > from a real device? > > > > That seems uselessly complicated to me. > > Well I too do not understand why OP can't just fail one existing > device, but it seemed important to them to experience actual errors > and have it kicked out for that. A half way measure might be the > offline / delete poking I mentioned in /sys/block. > > *shrug* > > Cheers, > Andy > > -- > https://bitfolk.com/ -- No-nonsense VPS hosting