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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 E7086C64E7A for ; Tue, 1 Dec 2020 11:35:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9CCA9206A5 for ; Tue, 1 Dec 2020 11:35:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730620AbgLALfW (ORCPT ); Tue, 1 Dec 2020 06:35:22 -0500 Received: from smtp.hosts.co.uk ([85.233.160.19]:26706 "EHLO smtp.hosts.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727165AbgLALfW (ORCPT ); Tue, 1 Dec 2020 06:35:22 -0500 Received: from host86-149-69-253.range86-149.btcentralplus.com ([86.149.69.253] helo=[192.168.1.64]) by smtp.hosts.co.uk with esmtpa (Exim) (envelope-from ) id 1kk3vc-000Cfy-4i; Tue, 01 Dec 2020 11:34:40 +0000 Subject: Re: Fwd: [OT][X-POST] RAID-6 hw rebuild speed To: Gandalf Corvotempesta , General discussion - ask "questions," receive answers and advice from other ZFS users , Linux RAID Mailing List References: From: Wols Lists X-Enigmail-Draft-Status: N1110 Message-ID: <5FC62A4F.9000100@youngman.org.uk> Date: Tue, 1 Dec 2020 11:34:39 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On 01/12/20 09:57, Gandalf Corvotempesta wrote: > Sorry for the OT and X-POST but these 2 lists are full of skilled > storage engineer. > For a very,very,very,very long time I used 15k SAS 3.5'' disks. A > RAID-6 hardware (8 disks) took about 20 hours to rebuild. > > Now I've replaced a 3.5 disks with a 15k SAS 2.5'' disk. raid is > rebuilding properly, but the ETA is less then 1 hours. > > I've moved from a 20 hours rebuild to about 50 minutes rebuild, by > just changing one 3.5' disks with a 2.5' > > Is this normal ? I'm thinking something strange is happening > Your rebuild time is effectively the time it takes to write to the new disk. So I'm guessing if you had to wipe and rebuild one of the old disks it would again be 20 hours. So what's different about the new disk? Yes I know it's a 2.5". But could it be it's SATA-3 as opposed to the old ones being SATA-2? There's a whole bunch of things it could be. But my money's on it having a bigger cache. The ETA is based on how fast it can read from the existing array and the rebuild hasn't yet filled the cache. Once that fills up and the disk write speed kicks in, the ETA will start climbing fast as the write speed starts dominating the ETA. That said, it'll probably be faster than the old 20hrs, but I don't know by how much. Cheers, Wol