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 89A1CC4332F for ; Wed, 19 Oct 2022 21:25:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229991AbiJSVZM (ORCPT ); Wed, 19 Oct 2022 17:25:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37624 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229973AbiJSVZJ (ORCPT ); Wed, 19 Oct 2022 17:25:09 -0400 Received: from smtp.hosts.co.uk (smtp.hosts.co.uk [85.233.160.19]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CCDB91217C4 for ; Wed, 19 Oct 2022 14:25:06 -0700 (PDT) Received: from host86-161-232-249.range86-161.btcentralplus.com ([86.161.232.249] helo=[192.168.1.218]) by smtp.hosts.co.uk with esmtpa (Exim) (envelope-from ) id 1olGYj-000All-A0; Wed, 19 Oct 2022 22:25:05 +0100 Message-ID: <7ca2b272-4920-076f-ecaf-5109db0aae46@youngman.org.uk> Date: Wed, 19 Oct 2022 22:25:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.1 Subject: Re: Performance Testing MD-RAID10 with 1 failed drive To: Reindl Harald , Umang Agarwalla , linux-raid@vger.kernel.org References: Content-Language: en-GB From: Wols Lists In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On 19/10/2022 22:00, Reindl Harald wrote: > > > Am 19.10.22 um 21:30 schrieb Umang Agarwalla: >> Hello all, >> >> We run Linux RAID 10 in our production with 8 SAS HDDs 7200RPM. >> We recently got to know from the application owners that the writes on >> these machines get affected when there is one failed drive in this >> RAID10 setup, but unfortunately we do not have much data around to >> prove this and exactly replicate this in production. >> >> Wanted to know from the people of this mailing list if they have ever >> come across any such issues. >> Theoretically as per my understanding a RAID10 with even a failed >> drive should be able to handle all the production traffic without any >> issues. Please let me know if my understanding of this is correct or >> not. > > "without any issue" is nonsense by common sense No need for the sark. And why shouldn't it be "without any issue"? Common sense is usually mistaken. And common sense says to me the exact opposite - with a drive missing that's one fewer write, so if anything it should be quicker. Given that - on the system my brother was using - the ops guys didn't notice their raid-6 was missing TWO drives, it seems like lost drives aren't particularly noticeable by their absence ... Okay, with a drive missing it's DANGEROUS, but it should not have any noticeable impact on a production system until you replace the drive and it's rebuilding. Unfortunately, I don't know enough to say whether a missing drive would, or should, impact performance. Cheers, Wol