From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp161.vfemail.net (smtp161.vfemail.net [146.59.185.161]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E5F72AD2F for ; Tue, 3 Jun 2025 20:04:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=146.59.185.161 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748981062; cv=none; b=P9r47FvCp110pbOcaTORHRVvhoiy2tnE9jtf9NhZluVnl2XdzpBOnhzuc8z/nfAmpXKhXyaaQzTIZPVkEJmr58hC5IocCGPywfHXTeHR956Ir2jafX0cQkNtteYz/LjKHu1mm8s/IoLMajQ2Chv9cLna/WvkEb1ZUh/rmFlelbw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748981062; c=relaxed/simple; bh=JYj1vNTn15og/+5O5aPag3/4oCOhC1CSroGuCvxIsKI=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=qJv7bX/sYsPUXRuOnvXzRM0IOgGhXIGDVvRJ0zZHp0fzt0yHoziPT3YmARJuANn4WnQsxoVe6/YVmmoJEXndwqP7YQHN8TWtJ+9mVsWVpckpCIYzjZKb9CEJqBFIv4PlqApQG31QFbgbMvoktt8K7FjWWJWgjSbNMoU0fIQSESc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=vfemail.net; spf=pass smtp.mailfrom=vfemail.net; dkim=pass (1024-bit key) header.d=vfemail.net header.i=@vfemail.net header.b=Jls2wNlo; arc=none smtp.client-ip=146.59.185.161 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=vfemail.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=vfemail.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=vfemail.net header.i=@vfemail.net header.b="Jls2wNlo" Received: (qmail 10002 invoked from network); 3 Jun 2025 20:03:01 +0000 Received: from localhost (HELO nl101-3.vfemail.net) () by smtpout.vfemail.net with SMTP; 3 Jun 2025 20:03:01 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=simple; d=vfemail.net; h=date:from :to:cc:subject:message-id:in-reply-to:references:mime-version :content-type:content-transfer-encoding; s=2018; bh=JYj1vNTn15og /+5O5aPag3/4oCOhC1CSroGuCvxIsKI=; b=Jls2wNlolwH3k8VTnQGr9TY2i4bd JU9qdw/PzC3spTY+G/dqB14s7b/Xq4XZNteafluH3d7zNxw+ZMHGmFLQQSfYWGkG 4IOYrCjBCa7UnQMVk/5SHDBeIlsXlO4UfoH3ol7GjERAURAT0nVNxDRnfOkDD2UY f9iuVYGX2Mvhhwg= Received: (qmail 30415 invoked from network); 3 Jun 2025 15:04:17 -0500 Received: by simscan 1.4.0 ppid: 30392, pid: 30408, t: 0.3477s scanners:none Received: from unknown (HELO bmwxMDEudmZlbWFpbC5uZXQ=) (aGdudGt3aXNAdmZlbWFpbC5uZXQ=@MTkyLjE2OC4xLjE5Mg==) by nl101.vfemail.net with ESMTPA; 3 Jun 2025 20:04:17 -0000 Date: Tue, 3 Jun 2025 16:04:15 -0400 From: David Niklas To: Wol Cc: Linux RAID , linux-kernel@vger.kernel.org Subject: Re: Need help increasing raid scan efficiency. Message-ID: <20250603160415.61c9ca7c@Zen-II-x12.niklas.com> In-Reply-To: <24815d81-2e4f-4ddf-b194-b03ea3232b91@youngman.org.uk> References: <20250602210514.7acd5325@Zen-II-x12.niklas.com> <24815d81-2e4f-4ddf-b194-b03ea3232b91@youngman.org.uk> X-Mailer: Claws Mail 4.3.0git38 (GTK 3.24.24; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 3 Jun 2025 17:46:01 +0100 Wol wrote: > On 03/06/2025 02:05, David Niklas wrote: > > So I setup the array into read-only mode and started the array with > > only two of the drives. Drives 0 and 1. Then I proceeded to try and > > start a second pair, drives 2 and 3, so that I could scan them > > simultaneously. With the intent of then switching it over to 0 and 2 > > and 1 and 3, then 0 and 3 and 1 and 2. > > BACKUP! BACKUP!! BACKUP!!! It's when I was trying to make my yearly backup that I found out it was corrupting. I have HDDs I backup to. When I backup, I erase the previous year (as I don't have enough room otherwise), then backup the new year. As a system, it worked up until now. > Is your array that messed up that it won't assemble? If you can just > get it to assemble normally that's your best bet by far. Trying to > assemble it as two pairs is throwing away the whole point of a raid 6! It assembles fine with all the disks, the problem is the data corruption that has occurred across the members. > And make sure you know the order of the drives in the array! I hope you > haven't lost that infof. Everything is written down on paper. > If your event counts are all similar, then you'll hopefully recover > most of your data. Your biggest worry will be the mobo and ram having > trashing an in-flight write that corrupts the disk. Yes, that's my problem. I wanted to try and isolate the disk pairs so that I could try and figure out if there is any pattern or differing copies that would allow me to restore the corrupted data. > Then once you've got the array assembled, I can't remember the command, > but there is a command that will read the entire stripe, check the > paritIES - both of them, and recreate the data. If that fails, your > data is probably toast, and nothing you can do will be able to retrieve > much :-( > > Cheers, > Wol > Searching online turned up raid6check. https://unix.stackexchange.com/questions/137384/raid6-scrubbing-mismatch-repair But the people there also pointed out that Linux's raid repair operation only recalculates the parity. I would have thought that it did a best of 3 option. I mean, that's a big part of why we have RAID6 instead of RAID5, right? I think you misunderstood my original question, how do I assemble the RAID6 pairs (RO mode) into two different arrays such that I can read from them simultaneously? If I have to do some coding with respect to the mdadm utility, I'm willing. But for all I know, the Linux Kernel might destroy all of my data if I try something like that. Thanks, David From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp161.vfemail.net (smtp161.vfemail.net [146.59.185.161]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0CD14A23 for ; Tue, 3 Jun 2025 20:04:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=146.59.185.161 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748981087; cv=none; b=hTf09A1WvjBngToD6xT6TGYTIYYSiXECQjlou6v0hOQgLcKGR2pNLrvUQHHM3W/PTV1GD52ISbOJJoAGHD73Uz35hBx3huZ4gYHp9T9wTgW8mgP4bMu+DO8jn0cFfOyEP/SzSQ0KbjrUf0II535ovHxiZfryV0Ur+TYVktUqZFk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748981087; c=relaxed/simple; bh=JYj1vNTn15og/+5O5aPag3/4oCOhC1CSroGuCvxIsKI=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mNsq+nrtiTt2ExV8M5Yvp9GQy2iW4ZDdddzBFs1Yr8mK7H3OJ3f81kwfQ+5qmHQEVt36NkwYWnZCWF6PP34uemsFifaZ38IwJ3ViRyv14HQwHbnQ2u/ZaoGJdTYO+rd2KCdHXQSS8HEskH/ZQfQebTcpa9IpsbTgKOggkCOYx+o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=vfemail.net; spf=pass smtp.mailfrom=vfemail.net; dkim=pass (1024-bit key) header.d=vfemail.net header.i=@vfemail.net header.b=on3tHABe; arc=none smtp.client-ip=146.59.185.161 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=vfemail.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=vfemail.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=vfemail.net header.i=@vfemail.net header.b="on3tHABe" Received: (qmail 10198 invoked from network); 3 Jun 2025 20:03:26 +0000 Received: from localhost (HELO nl101-3.vfemail.net) () by smtpout.vfemail.net with SMTP; 3 Jun 2025 20:03:26 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=simple; d=vfemail.net; h=date:from :to:cc:subject:message-id:in-reply-to:references:mime-version :content-type:content-transfer-encoding; s=2018; bh=JYj1vNTn15og /+5O5aPag3/4oCOhC1CSroGuCvxIsKI=; b=on3tHABexCSlgcrXYMYanqqtQPib Hb9iFFqBFDDNS6e0W47drU4hICW9uq332nXgJYdvKOKyfeXms5Lwf5h9RG5S3tnr xP35/kd1Aaxzo/BHPfZD1VzCD10bgTG1BE0YsyCVGizN9c1wEzTmDxPc4t+VN2fh 5uCAsDse6RRhGZg= Received: (qmail 31100 invoked from network); 3 Jun 2025 15:04:43 -0500 Received: by simscan 1.4.0 ppid: 30998, pid: 31085, t: 0.3395s scanners:none Received: from unknown (HELO bmwxMDEudmZlbWFpbC5uZXQ=) (aGdudGt3aXNAdmZlbWFpbC5uZXQ=@MTkyLjE2OC4xLjE5Mg==) by nl101.vfemail.net with ESMTPA; 3 Jun 2025 20:04:43 -0000 Date: Tue, 3 Jun 2025 16:04:40 -0400 From: David Niklas To: Linux RAID Cc: linux-kernel@vger.kernel.org Subject: Re: Need help increasing raid scan efficiency. Message-ID: <20250603160415.61c9ca7c@Zen-II-x12.niklas.com> In-Reply-To: <24815d81-2e4f-4ddf-b194-b03ea3232b91@youngman.org.uk> References: <20250602210514.7acd5325@Zen-II-x12.niklas.com> <24815d81-2e4f-4ddf-b194-b03ea3232b91@youngman.org.uk> X-Mailer: Claws Mail 4.3.0git38 (GTK 3.24.24; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID: <20250603200440.H9NzN4tlI-91FzsXaXnLrZ3IJQrIa35hE8Ax3NfI3t4@z> On Tue, 3 Jun 2025 17:46:01 +0100 Wol wrote: > On 03/06/2025 02:05, David Niklas wrote: > > So I setup the array into read-only mode and started the array with > > only two of the drives. Drives 0 and 1. Then I proceeded to try and > > start a second pair, drives 2 and 3, so that I could scan them > > simultaneously. With the intent of then switching it over to 0 and 2 > > and 1 and 3, then 0 and 3 and 1 and 2. > > BACKUP! BACKUP!! BACKUP!!! It's when I was trying to make my yearly backup that I found out it was corrupting. I have HDDs I backup to. When I backup, I erase the previous year (as I don't have enough room otherwise), then backup the new year. As a system, it worked up until now. > Is your array that messed up that it won't assemble? If you can just > get it to assemble normally that's your best bet by far. Trying to > assemble it as two pairs is throwing away the whole point of a raid 6! It assembles fine with all the disks, the problem is the data corruption that has occurred across the members. > And make sure you know the order of the drives in the array! I hope you > haven't lost that infof. Everything is written down on paper. > If your event counts are all similar, then you'll hopefully recover > most of your data. Your biggest worry will be the mobo and ram having > trashing an in-flight write that corrupts the disk. Yes, that's my problem. I wanted to try and isolate the disk pairs so that I could try and figure out if there is any pattern or differing copies that would allow me to restore the corrupted data. > Then once you've got the array assembled, I can't remember the command, > but there is a command that will read the entire stripe, check the > paritIES - both of them, and recreate the data. If that fails, your > data is probably toast, and nothing you can do will be able to retrieve > much :-( > > Cheers, > Wol > Searching online turned up raid6check. https://unix.stackexchange.com/questions/137384/raid6-scrubbing-mismatch-repair But the people there also pointed out that Linux's raid repair operation only recalculates the parity. I would have thought that it did a best of 3 option. I mean, that's a big part of why we have RAID6 instead of RAID5, right? I think you misunderstood my original question, how do I assemble the RAID6 pairs (RO mode) into two different arrays such that I can read from them simultaneously? If I have to do some coding with respect to the mdadm utility, I'm willing. But for all I know, the Linux Kernel might destroy all of my data if I try something like that. Thanks, David