From owner-freebsd-stable@FreeBSD.ORG Fri Oct 17 08:10:49 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 CF16DA9D; Fri, 17 Oct 2014 08:10:49 +0000 (UTC) Received: from mail-yk0-x22c.google.com (mail-yk0-x22c.google.com [IPv6:2607:f8b0:4002:c07::22c]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 8374934C; Fri, 17 Oct 2014 08:10:49 +0000 (UTC) Received: by mail-yk0-f172.google.com with SMTP id 19so131898ykq.31 for ; Fri, 17 Oct 2014 01:10:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=6pHgM4ewGGmMIsEJknaV3l3dKBM89/tegH9AL4LAu88=; b=w4TNzUZJdZnFNLvux770E+kfeXnHn2I6VrVMhzqwo+Ni/WDONZ9mFSxIYFMgZDE5hW +P13ZShd+g1MbS/FQ61e0L2kN42CidgsuKbvaPr3aE8fcBUkDdK+gm1w5mK90Oc6D9TT NlJyqyJiNZbbr9Nr3vg46sjqz1JQK9izT0nx/iLyEe292QYjVPcUW+Z/oFF48gUXAObv pImAU8sz1zzyAWNwgjM1N0NpdjgEJ+4qcHkg98lCripngDcKYo3LpBysKHrlLGYaFMjo O+vAQ4ihC7qNWrdDqWAmALvAYJOmel2Yj63YFRJUzlEQcoKO8VTRZ1fJDt53rmw528T3 lV/A== MIME-Version: 1.0 X-Received: by 10.236.16.230 with SMTP id h66mr2162342yhh.145.1413533448616; Fri, 17 Oct 2014 01:10:48 -0700 (PDT) Received: by 10.170.156.139 with HTTP; Fri, 17 Oct 2014 01:10:48 -0700 (PDT) In-Reply-To: <201410132047.s9DKlGxD030176@gw.catspoiler.org> References: <43D94A22FBD2477FBBDEFF16C0088DDA@multiplay.co.uk> <201410132047.s9DKlGxD030176@gw.catspoiler.org> Date: Fri, 17 Oct 2014 09:10:48 +0100 Message-ID: Subject: Re: getting to 4K disk blocks in ZFS From: krad To: Don Lewis Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.18-1 Cc: freebsd-stable , Steven Hartland , fullermd@over-yonder.net 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: Fri, 17 Oct 2014 08:10:49 -0000 your also forgetting you can enable compression, which on mail files will give you a large ratio On 13 October 2014 21:47, Don Lewis wrote: > On 13 Oct, Steven Hartland wrote: > > ----- 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/ > > This is a timely subject. I'm planning on moving my Cyrus imap mail > spool from a 4K/1K UFS filesystem to a three drive raidz1. It looks > like the UFS fragmentation overhead is about 2.4%. ZFS ashift=12 > increases that to about 17%. Combine that with raidz and now the > overhead is about 40%. Ouch! > > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org" >