From owner-freebsd-fs@FreeBSD.ORG Tue Aug 31 12:00:00 2010 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 D4A0C1065698 for ; Tue, 31 Aug 2010 12:00:00 +0000 (UTC) (envelope-from k0802647@telus.net) Received: from defout.telus.net (outbound04.telus.net [199.185.220.223]) by mx1.freebsd.org (Postfix) with ESMTP id 9193F8FC13 for ; Tue, 31 Aug 2010 12:00:00 +0000 (UTC) Received: from edtnaa02.telusplanet.net ([66.183.53.162]) by priv-edtnes24.telusplanet.net (InterMail vM.7.09.01.00 201-2219-108-20080618) with ESMTP id <20100831110906.ZHEE6754.priv-edtnes24.telusplanet.net@edtnaa02.telusplanet.net> for ; Tue, 31 Aug 2010 05:09:06 -0600 Received: from oliver.bc.lan (d66-183-53-162.bchsia.telus.net [66.183.53.162]) by edtnaa02.telusplanet.net (BorderWare Security Platform) with ESMTP id 61E791E2A3BCDCF2 for ; Tue, 31 Aug 2010 05:09:05 -0600 (MDT) Received: from [10.111.111.112] (unknown [10.111.111.112]) by oliver.bc.lan (Postfix) with ESMTP id 493666455; Tue, 31 Aug 2010 04:09:05 -0700 (PDT) Message-ID: <4C7CE2D0.40400@telus.net> Date: Tue, 31 Aug 2010 04:09:04 -0700 From: Carl User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.7) Gecko/20100713 Lightning/1.0b2 Thunderbird/3.1.1 MIME-Version: 1.0 To: freebsd-fs@freebsd.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Cloudmark-Analysis: v=1.1 cv=SJIhyCEJBCHyullCFvS0mIdE5QsJS0d45teFqlr0wtg= c=1 sm=0 a=SHg4dW30_F4A:10 a=8nJEP1OIZ-IA:10 a=HNgjH8kF64GtJ7EcXKEMsQ==:17 a=_N190bLxhghOylsEThsA:9 a=JMHaxkYw0aMDhDWIOe2RIzOVwJEA:4 a=wPNLvfGTeEIA:10 a=HpAAvcLHHh0Zw7uRqdWCyQ==:117 X-Mailman-Approved-At: Tue, 31 Aug 2010 12:11:16 +0000 Subject: gjournal alignment on 4K sector advanced format drives 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: Tue, 31 Aug 2010 12:00:00 -0000 My understanding is that I can avoid misalignment-induced performance problems with Western Digital WDxxEARS drives (4KiB physical sector size) by ensuring two things: 1. GPT partitions are aligned to 4KiB boundaries, and 2. Use "newfs -b 32768 -f 4096 ..." so that UFS2 fragments are not smaller than the physical sector size. True? Now I want to add gjournal to some of my partitions. It seems to me that I must also ensure the journal is aligned just as I've done with the data. So far, though, I have found no information as to how the journal's own filesystem layout works. Does it use fixed size blocks/fragments like the UFS2 data does? If so, what is its minimum addressable unit size? If it is smaller than 4KiB, we get journal misalignment and a performance loss, right? What must I do to ensure the journal is fully aligned? In the past I've put the data and journal on the same provider, but I am unsure whether a specified size for the journal is accurately observed. If I specify a 1GiB journal, will I get exactly that? My concern is whether an added/subtracted sector might be used for some kind of journal header, thereby throwing off the alignment of the journal again. Is it better to put the journal on its own provider (ie. separate partition) to aid alignment in some way? What are the pros and cons for shared vs. separate providers in general? Carl / K0802647