From owner-freebsd-hackers@FreeBSD.ORG Mon Jun 2 17:20:10 2014 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 40BEB227; Mon, 2 Jun 2014 17:20:10 +0000 (UTC) Received: from d.mail.sonic.net (d.mail.sonic.net [64.142.111.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 231BA2E72; Mon, 2 Jun 2014 17:20:09 +0000 (UTC) Received: from aurora.physics.berkeley.edu (aurora.Physics.Berkeley.EDU [128.32.117.67]) (authenticated bits=0) by d.mail.sonic.net (8.14.4/8.14.4) with ESMTP id s52HK7nD016453 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT); Mon, 2 Jun 2014 10:20:07 -0700 Message-ID: <538CB246.9080905@freebsd.org> Date: Mon, 02 Jun 2014 10:20:06 -0700 From: Nathan Whitehorn User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: "Justin T. Gibbs" , Mark Felder Subject: Re: fdisk(8) vs gpart(8), and gnop References: <20140601004242.GA97224@bewilderbeast.blackhelicopters.org> <3D6974D83AE9495E890D9F3CA654FA94@multiplay.co.uk> <538B4CEF.2030801@freebsd.org> <1DB2D63312CE439A96B23EAADFA9436E@multiplay.co.uk> <538B4FD7.4090000@freebsd.org> <538C9207.9040806@freebsd.org> <61DC020F-F061-4A6E-AAEA-F0AE4CAE92F9@scsiguy.com> In-Reply-To: <61DC020F-F061-4A6E-AAEA-F0AE4CAE92F9@scsiguy.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit X-Sonic-ID: C;eqR8JHrq4xGzasUoeQW9yA== M;MIimJHrq4xGzasUoeQW9yA== Cc: freebsd-fs@freebsd.org, FreeBSD Hackers , Matthew Ahrens , owner-freebsd-fs@freebsd.org X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 Jun 2014 17:20:10 -0000 On 06/02/14 10:15, Justin T. Gibbs wrote: > On Jun 2, 2014, at 9:49 AM, Mark Felder wrote: > >> On 2014-06-02 10:02, Nathan Whitehorn wrote: >>> My bigger concern is this pool upgrade one -- what if someone puts in >>> a 4K disk in the future? >> This is a concern of mine, and I sort of wish we did 4k by default and forced people to override if they want 512b or something else. > Adding a 4k sectored device is fine. You just need to use it in a new top-level vdev in the pool. > > If you are at the point where you can’t get new or compatible warrantee replacements for the drives that may fail in your existing pool, you should be migrating your data to new devices anyway. Mixing devices with different performance characteristics within a TLV can lead to pessimal behavior. I don’t think that ZFS should jump through large hoops to try and make this work well. Instead, we should encourage the use of similar devices within a TLV (guidance that the installer has sufficient information to provide*) and the system should be optimized assuming this is how it will be used. > > I certainly *do not* want FreeBSD to automatically inflate the ashift used on my pools. Doing so is an attempt to guess why I chose the devices I did at pool creation time and my strategy for retiring them in the future. The current proposal guesses wrong for me and the products I help build. I’d bet it will be wrong more times than right. > > — > Justin > > *) Using the tools already in FreeBSD it is quite easy to group devices by transport type, capacity, logical block size, physical block size, and, for at least SCSI transports, media rotational speed. We do this in Spectra’s ZFS appliance so users have to work really hard to mix devices that they shouldn’t. > Well, this makes it sound easy then. We just don't worry about it and keep the existing defaults. This requires some documentation updates and changes to the installer. The "standard" advice seems to be universally to add gnops to set the sector size to 4k and the existing installer ZFS support does this. -Nathan