From owner-freebsd-stable@FreeBSD.ORG Mon Dec 9 07:15:17 2013 Return-Path: Delivered-To: freebsd-stable@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 660456DC; Mon, 9 Dec 2013 07:15:17 +0000 (UTC) Received: from smtp.fagskolen.gjovik.no (smtp.fagskolen.gjovik.no [IPv6:2001:700:1100:1:200:ff:fe00:b]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id C7D141AB5; Mon, 9 Dec 2013 07:15:16 +0000 (UTC) Received: from mail.fig.ol.no (localhost [127.0.0.1]) by mail.fig.ol.no (8.14.7/8.14.7) with ESMTP id rB97FDX4031990 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 9 Dec 2013 08:15:13 +0100 (CET) (envelope-from trond@fagskolen.gjovik.no) Received: from localhost (trond@localhost) by mail.fig.ol.no (8.14.7/8.14.7/Submit) with ESMTP id rB97FDvg031987; Mon, 9 Dec 2013 08:15:13 +0100 (CET) (envelope-from trond@fagskolen.gjovik.no) X-Authentication-Warning: mail.fig.ol.no: trond owned process doing -bs Date: Mon, 9 Dec 2013 08:15:13 +0100 (CET) From: =?ISO-8859-1?Q?Trond_Endrest=F8l?= Sender: Trond.Endrestol@fagskolen.gjovik.no To: Mark Felder Subject: Re: Does FreeBSD's ZFS reserve 1/64 of the capacity for COW? In-Reply-To: <1386350612.24515.56413717.7535920E@webmail.messagingengine.com> Message-ID: References: <1386350612.24515.56413717.7535920E@webmail.messagingengine.com> User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) Organization: Fagskolen Innlandet OpenPGP: url=http://fig.ol.no/~trond/trond.key MIME-Version: 1.0 Content-ID: X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED autolearn=unavailable version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on mail.fig.ol.no Content-Type: TEXT/PLAIN; CHARSET=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-Content-Filtered-By: Mailman/MimeDel 2.1.17 Cc: freebsd-stable@freebsd.org X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.17 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, 09 Dec 2013 07:15:17 -0000 On Fri, 6 Dec 2013 11:23-0600, Mark Felder wrote: > > > On Fri, Dec 6, 2013, at 6:46, Trond Endrestøl wrote: > > Hi, > > > > Today I came across "Becoming a ZFS Ninja Part 1" > > http://www.youtube.com/watch?v=tPsV_8k-aVU featuring Ben Rockwood who > > stated that ZFS reserves 1/64 of the capacity for COW safe-guarding. > > Fast forward to 00:49:44. Thus, one should take this fact into account > > when planning the storage capacity of your (larger) zpools. > > > > Does FreeBSD's ZFS also reserve 1/64 of the capacity for COW? > > > > If it's true, then I guess this should be noted in zpool(8) and in the > > Handbook. > > > > Well, the rule-of-thumb / urban legend tends to be "don't let your zpool > go over ~80% or you'll have severe performance issues" so I'm not sure > that statement is accurate or COW wouldn't be so painful when your pool > is over ~80%. I could be wrong though; I often am :-) As it turns out, you're in good company, I'm also wrong far too often. -- +-------------------------------+------------------------------------+ | Vennlig hilsen, | Best regards, | | Trond Endrestøl, | Trond Endrestøl, | | IT-ansvarlig, | System administrator, | | Fagskolen Innlandet, | Gjøvik Technical College, Norway, | | tlf. mob. 952 62 567, | Cellular...: +47 952 62 567, | | sentralbord 61 14 54 00. | Switchboard: +47 61 14 54 00. | +-------------------------------+------------------------------------+