From owner-freebsd-stable@FreeBSD.ORG Mon Oct 13 19:22:37 2014 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 69AEF284 for ; Mon, 13 Oct 2014 19:22:37 +0000 (UTC) Received: from smtp1.multiplay.co.uk (smtp1.multiplay.co.uk [85.236.96.35]) by mx1.freebsd.org (Postfix) with ESMTP id 2CEEE365 for ; Mon, 13 Oct 2014 19:22:36 +0000 (UTC) Received: by smtp1.multiplay.co.uk (Postfix, from userid 65534) id 6CA9520E708EE; Mon, 13 Oct 2014 19:22:36 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.multiplay.co.uk X-Spam-Level: ** X-Spam-Status: No, score=2.2 required=8.0 tests=AWL,BAYES_00,DOS_OE_TO_MX, FSL_HELO_NON_FQDN_1,RDNS_DYNAMIC,STOX_REPLY_TYPE autolearn=no version=3.3.1 Received: from r2d2 (82-69-141-170.dsl.in-addr.zen.co.uk [82.69.141.170]) by smtp1.multiplay.co.uk (Postfix) with ESMTPS id 7DF5B20E708EC; Mon, 13 Oct 2014 19:22:34 +0000 (UTC) Message-ID: <43D94A22FBD2477FBBDEFF16C0088DDA@multiplay.co.uk> From: "Steven Hartland" To: "Matthew D. Fuller" , "freebsd-stable" References: <540FF3C4.6010305@ish.com.au> <54100258.2000505@freebsd.org> <5410F0B4.9040808@ish.com.au> <543C1E7B.4090204@bluerosetech.com> <20141013191903.GR2161@over-yonder.net> Subject: Re: getting to 4K disk blocks in ZFS Date: Mon, 13 Oct 2014 20:22:31 +0100 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Oct 2014 19:22:37 -0000 ----- Original Message ----- From: "Matthew D. Fuller" > On Mon, Oct 13, 2014 at 11:48:27AM -0700 I heard the voice of > Darren Pilgrim, and lo! it spake thus: >> >> If the default is 4k and (for the limited time they're still common) >> you use true 512b disks, you can waste space. Sure, but how much >> space? > > The median file in /usr/ports is 408 bytes. Over 90% of the files are > under 2k, which means the wastage for them is over 100% (before > counting what gain compression might get). A little offhand mathery > says it's about 78% extra overhead on the whole. > > And that includes the almost hundred megs (over 22% of the total size > of the FS) for the INDEX.db, plus the ~90 megs of the flat INDEX files > (another 20%). If you pull those out, the overhead is 130%. > > > (To be sure, relatively few people have ports trees eating most of > their space, but still; it's pretty pathological. I for one did > decide some years back to always force 4k on any new FSen to make > future life simpler, accepting the bloat, but it's there.) And thats before you add the overhead if your running RAIDZ... A good read on this is http://blog.delphix.com/matt/2014/06/06/zfs-stripe-width/ Regards Steve