From owner-freebsd-stable@FreeBSD.ORG Fri Dec 6 12:47:02 2013 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 928FF6EA for ; Fri, 6 Dec 2013 12:47:02 +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 04D2818EA for ; Fri, 6 Dec 2013 12:47:01 +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 rB6Ckvkj098953 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Fri, 6 Dec 2013 13:46:57 +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 rB6CkuOv098950 for ; Fri, 6 Dec 2013 13:46:57 +0100 (CET) (envelope-from trond@fagskolen.gjovik.no) X-Authentication-Warning: mail.fig.ol.no: trond owned process doing -bs Date: Fri, 6 Dec 2013 13:46:56 +0100 (CET) From: =?ISO-8859-1?Q?Trond_Endrest=F8l?= Sender: Trond.Endrestol@fagskolen.gjovik.no To: FreeBSD stable Subject: Does FreeBSD's ZFS reserve 1/64 of the capacity for COW? Message-ID: 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 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 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: Fri, 06 Dec 2013 12:47:02 -0000 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. Any comments or insights? Do you think I should file a PR? Have a nice weekend! ;-) -- +-------------------------------+------------------------------------+ | 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. | +-------------------------------+------------------------------------+