From owner-freebsd-questions@freebsd.org Sat Oct 21 21:08:12 2017 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 1AF93E3A519 for ; Sat, 21 Oct 2017 21:08:12 +0000 (UTC) (envelope-from 4250.10.freebsd-questions=freebsd.org@email-od.com) Received: from bca5.email-od.com (bca5.email-od.com [207.246.239.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id E02D56BF56 for ; Sat, 21 Oct 2017 21:08:11 +0000 (UTC) (envelope-from 4250.10.freebsd-questions=freebsd.org@email-od.com) DKIM-Signature: v=1; a=rsa-sha256; d=email-od.com;i=@email-od.com;s=dkim; c=relaxed/relaxed; q=dns/txt; t=1508620085; x=1511212085; h=x-thread-info:date:from:to:subject:message-id:in-reply-to:references:mime-version:content-type:content-transfer-encoding; bh=CgOC3Rc+Wg/o+1mAtqnihskFTwj2bW4hoWIVQRF9uxc=; b=RoRiiGPBbE9FOj71hN0py09/qH9S2XjtN68qCUtOOi0ac+4DgPFROwlr2MF0MDrvtRnAKI1PZCZK+Ewo1gRbtzBelkdPynrtCzt77XAX/fsVD0RU74EwvYNear2ty+DaxyeXQM8UcQybPhI6/76BLQB402cLEAytRlnVDjjYTm0= X-Thread-Info: NDI1MC4xMi5lNTAwMDAwMDQ0ZWVjMS5mcmVlYnNkLXF1ZXN0aW9ucz1mcmVlYnNkLm9yZw== Received: from r1.h.in.socketlabs.com (r1.h.in.socketlabs.com [142.0.180.11]) by bca2.email-od.com with ESMTP(version=Tls12 cipher=Aes256 bits=256); Sat, 21 Oct 2017 17:07:53 -0400 Received: from smtp.lan.sohara.org (EMTPY [89.127.62.20]) by r1.h.in.socketlabs.com with ESMTP(version=Tls12 cipher=Aes256 bits=256); Sat, 21 Oct 2017 17:07:58 -0400 Received: from [192.168.63.1] (helo=steve.lan.sohara.org) by smtp.lan.sohara.org with smtp (Exim 4.89 (FreeBSD)) (envelope-from ) id 1e60zs-000G75-99 for freebsd-questions@freebsd.org; Sat, 21 Oct 2017 21:07:56 +0000 Date: Sat, 21 Oct 2017 22:07:56 +0100 From: Steve O'Hara-Smith To: freebsd-questions@freebsd.org Subject: Re: How to recover data from dead hard drive. Message-Id: <20171021220756.c2df0a2c94298c985856e964@sohara.org> In-Reply-To: References: <59DBA387.4050108@gmail.com> <20171009191435.145c9dd2.freebsd@edvax.de> <72772933-C642-43DB-AFD6-6B5D40EEF39E@fjl.co.uk> <43621.128.135.52.6.1508425321.squirrel@cosmo.uchicago.edu> <4D114C69-A005-492B-B3A4-99A19CDF92E9@fjl.co.uk> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; amd64-portbld-freebsd11.0) X-Clacks-Overhead: "GNU Terry Pratchett" Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 21 Oct 2017 21:08:12 -0000 On Fri, 20 Oct 2017 10:11:21 +0000 Carmel NY wrote: > Personally, my confidence in hardware RAID far exceeds that of software > based RAID without regards to the OS. Of course, YMMV. In order of decreasing reliability: ZFS mirror - at least three ways ZFS raidz2 (perhaps equal in reliability to the mirror - but slower) Hardware mirror - at least three ways Hardware RAID6 Software mirror - at least three ways Software RAID6 Anything without at least two drive redundancy is not reliable IMHO, when a drive fails you have no redundancy until a replacement is installed and populated - which is bad enough if you have a hot spare but if you have to wait for an order cycle or worse yet for an RMA that can be an uncomfortably long time to be at risk. Hardware falls behind ZFS mainly because of the protection against silent corruption in ZFS and raidz2 lacking the write hole of RAID6. -- Steve O'Hara-Smith