From owner-freebsd-hackers@FreeBSD.ORG Mon Jun 2 17:15:53 2014 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id F1D5AFF1; Mon, 2 Jun 2014 17:15:52 +0000 (UTC) Received: from aslan.scsiguy.com (aslan.scsiguy.com [70.89.174.89]) (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 A21102E32; Mon, 2 Jun 2014 17:15:52 +0000 (UTC) Received: from jt-mbp.sldomain.com (207-225-98-3.dia.static.qwest.net [207.225.98.3]) (authenticated bits=0) by aslan.scsiguy.com (8.14.8/8.14.8) with ESMTP id s52HFlxG018167 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Mon, 2 Jun 2014 11:15:49 -0600 (MDT) (envelope-from gibbs@scsiguy.com) Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.2\)) Subject: Re: fdisk(8) vs gpart(8), and gnop From: "Justin T. Gibbs" In-Reply-To: Date: Mon, 2 Jun 2014 11:15:42 -0600 Content-Transfer-Encoding: quoted-printable Message-Id: <61DC020F-F061-4A6E-AAEA-F0AE4CAE92F9@scsiguy.com> 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> To: Mark Felder X-Mailer: Apple Mail (2.1878.2) Cc: freebsd-fs@freebsd.org, FreeBSD Hackers , Matthew Ahrens , owner-freebsd-fs@freebsd.org, Nathan Whitehorn 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 17:15:53 -0000 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? >=20 > 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=92t 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=92t 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=92d bet it will be wrong more times than right. =97 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=92s ZFS appliance so users have to work really hard to mix = devices that they shouldn=92t.=