From owner-freebsd-fs@FreeBSD.ORG Thu Oct 13 21:49:03 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4A11D106566B for ; Thu, 13 Oct 2011 21:49:03 +0000 (UTC) (envelope-from bfriesen@simple.dallas.tx.us) Received: from blade.simplesystems.org (blade.simplesystems.org [65.66.246.74]) by mx1.freebsd.org (Postfix) with ESMTP id 0D0B98FC0C for ; Thu, 13 Oct 2011 21:49:02 +0000 (UTC) Received: from freddy.simplesystems.org (freddy.simplesystems.org [65.66.246.65]) by blade.simplesystems.org (8.14.4+Sun/8.14.4) with ESMTP id p9DLn15R013175; Thu, 13 Oct 2011 16:49:01 -0500 (CDT) Date: Thu, 13 Oct 2011 16:49:01 -0500 (CDT) From: Bob Friesenhahn X-X-Sender: bfriesen@freddy.simplesystems.org To: Tom Evans In-Reply-To: Message-ID: References: <4E95AE08.7030105@lerctr.org> User-Agent: Alpine 2.01 (GSO 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (blade.simplesystems.org [65.66.246.90]); Thu, 13 Oct 2011 16:49:02 -0500 (CDT) Cc: freebsd-fs@freebsd.org, Johannes Totz Subject: Re: AF (4096 byte sector) drives: Can you mix/match in a ZFS pool? X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 13 Oct 2011 21:49:03 -0000 On Thu, 13 Oct 2011, Tom Evans wrote: > On Thu, Oct 13, 2011 at 3:27 PM, Larry Rosenman wrote: >> I think something(tm) should be put in the handbook about this. > > TBH I think that ZFS should just move it's default ashift to 11 and > have 4k blocks by default. Saves all this messing around with > temporary gnop devices. There is a cost to using 4k blocks becaus zfs metadata will then consume 4k bytes (each copy) rather than 512 bytes. As someone posted to the zfs-discuss list a few days ago, this consumes quite a lot of space when the zfs block size is set to 8K. This results in almost 2X the disk space consumption when using 8K zfs block size. There is additional performance cost because the drive will be doing I/O in 4K chunks rather than 512 byte chunks. Typical SAS enterprise drives (not near-line drives) are surely still all using small sectors because their storage size is not very high and to get more IOPS. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/