From owner-freebsd-questions@freebsd.org Thu Aug 31 14:18:01 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 3402EE1F87D for ; Thu, 31 Aug 2017 14:18:01 +0000 (UTC) (envelope-from frank2@fjl.co.uk) Received: from bs1.fjl.org.uk (bs1.fjl.org.uk [84.45.41.196]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "bs1.fjl.org.uk", Issuer "bs1.fjl.org.uk" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id D9FBE7DE26 for ; Thu, 31 Aug 2017 14:18:00 +0000 (UTC) (envelope-from frank2@fjl.co.uk) Received: from [10.4.242.25] ([46.233.78.25]) (authenticated bits=0) by bs1.fjl.org.uk (8.14.4/8.14.4) with ESMTP id v7VEHvbk004602 (version=TLSv1/SSLv3 cipher=DHE-DSS-AES128-SHA bits=128 verify=NO) for ; Thu, 31 Aug 2017 15:17:58 +0100 (BST) (envelope-from frank2@fjl.co.uk) Message-ID: <59A81A99.3040000@fjl.co.uk> Date: Thu, 31 Aug 2017 15:18:01 +0100 From: Frank Leonhardt Reply-To: frank2@fjl.co.uk Organization: Frank Leonhardt User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: freebsd-questions@freebsd.org Subject: Re: help creating new gmirror > 2TB References: <26f5e88e-1ea7-6332-ca5e-f055cfbdd280@fjl.co.uk> <59A7683F.5070102@gmail.com> In-Reply-To: <59A7683F.5070102@gmail.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Content-Filtered-By: Mailman/MimeDel 2.1.23 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: Thu, 31 Aug 2017 14:18:01 -0000 On 31/08/2017 02:37, JD wrote: > I thought that hdparm could work with the firmware to set the sector > size. > Not sure on this because hdparm has gone through a lot of modifications > over the years. > In the good old days, a sector was a sector! Fixed in to the disk by drilling a hole and shining a light through it as it spun past a sensor. IDE (aka S/ATA drives lie a LOT about what they're really doing. If you want them to pretend their sectors are 512b they will. But on the hardware they're fixed at 4K, so they read 4K in and throw away 3.5K. It gets bad if your OS is reading one sector at a time and the drive isn't caching it; and as the FS block size is unlikely to be 512b it gets fraught quite quickly. As you need an inter-sector gap and each sector has an ECC overhead that's not proportional to it's length, having larger physical sectors also means more of the disk is used for data and less for padding and overhead. Regards, Frank.