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 0B636C433ED for ; Fri, 14 May 2021 14:35:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DBD7A6141F for ; Fri, 14 May 2021 14:35:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234206AbhENOgo (ORCPT ); Fri, 14 May 2021 10:36:44 -0400 Received: from vps.thesusis.net ([34.202.238.73]:59760 "EHLO vps.thesusis.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234450AbhENOgn (ORCPT ); Fri, 14 May 2021 10:36:43 -0400 Received: from localhost (localhost [127.0.0.1]) by vps.thesusis.net (Postfix) with ESMTP id 01BFE21043; Fri, 14 May 2021 10:35:32 -0400 (EDT) Received: from vps.thesusis.net ([127.0.0.1]) by localhost (vps.thesusis.net [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id husKeRs7cn2j; Fri, 14 May 2021 10:35:31 -0400 (EDT) Received: by vps.thesusis.net (Postfix, from userid 1000) id BE45C21042; Fri, 14 May 2021 10:35:31 -0400 (EDT) References: <2140221131.2872520.1620837067395.JavaMail.zimbra@karlsbakk.net> <87a6oyr64b.fsf@vps.thesusis.net> <3f3fd663-77e4-8c23-eb22-1b8223eaf277@turmel.org> User-agent: mu4e 1.5.7; emacs 26.3 From: Phillip Susi To: Phil Turmel Cc: Roy Sigurd Karlsbakk , d tbsky , Linux Raid Subject: Re: raid10 redundancy Date: Fri, 14 May 2021 10:30:07 -0400 In-reply-to: <3f3fd663-77e4-8c23-eb22-1b8223eaf277@turmel.org> Message-ID: <87y2ch4c3w.fsf@vps.thesusis.net> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org Phil Turmel writes: > No, rebuild isn't just writing to the new disk. You have to read other > disks to get the data to write. In raid6, you must read at least n-2 > drives, compute, then write. In raid10, you just read the other drive > (or one of the other drives when copies>2), then write. Yes, but the data is striped across those multiple disks, so reading them in parallel takes no more time. At least unless you have a memory/bus bottleneck rather than a disk bottleneck. so again, you're probably right if you are using blazing fast NVME drives, but not for conventional HDD.