From owner-freebsd-stable@FreeBSD.ORG Mon Dec 9 15:33:20 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 ED2BBDE3 for ; Mon, 9 Dec 2013 15:33:20 +0000 (UTC) Received: from mail-ie0-f170.google.com (mail-ie0-f170.google.com [209.85.223.170]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id B354813B4 for ; Mon, 9 Dec 2013 15:33:20 +0000 (UTC) Received: by mail-ie0-f170.google.com with SMTP id qd12so6353200ieb.1 for ; Mon, 09 Dec 2013 07:33:13 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:sender:subject:mime-version:content-type:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to; bh=8IYQbG0vrvxUeyrqYXoHCWXGyDsQ84ZIldnzh/5S+3U=; b=cDkbwuE9IwqDG690XnTv9/74CB6qYkfZ2OtaVrnKmkKMf1J4hSnH+Lj+/M14wb6c5B SyT5TBxYw0K+k4QlSAUcqtbuiFf2L8pesVB9a3RDqc7XjICiYgVncJ03XBzyX6o3izZi 2jFWU0OnEPlhyShw9e3y1lnB9q65JuuMeZEKSlXzbhZku7nwmKAd1NbBArocDUBklgQN KoEIx1LUtZXcQ0YaRM9tVpw3+G4zAkhq5ItUNpWES2YF0FBbMF2RdJe/FzQVCCwghPGN NIFUKB7xMj6hDfjyjjoUZaDrytotgNu72jqxbKeG985xmm7+E3q/5h5/jZc4/vd2gAXZ JGRQ== X-Gm-Message-State: ALoCoQlWN6QFyw1Arm9Gz/6acdXKsAvipzFU6eHBcFz0IwiOnxO+tMZz7tRNEhWIJM3ykEdyNYeo X-Received: by 10.50.102.99 with SMTP id fn3mr15931201igb.5.1386603193771; Mon, 09 Dec 2013 07:33:13 -0800 (PST) Received: from fusion-mac.bsdimp.com (50-78-194-198-static.hfc.comcastbusiness.net. [50.78.194.198]) by mx.google.com with ESMTPSA id s4sm14323207ige.0.2013.12.09.07.33.12 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 09 Dec 2013 07:33:12 -0800 (PST) Sender: Warner Losh Subject: Re: Does FreeBSD's ZFS reserve 1/64 of the capacity for COW? Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: text/plain; charset=iso-8859-1 From: Warner Losh In-Reply-To: Date: Mon, 9 Dec 2013 08:33:11 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: <01D335F5-1B57-4B3E-BE78-38794F65B7A9@bsdimp.com> References: <1386350612.24515.56413717.7535920E@webmail.messagingengine.com> To: =?iso-8859-1?Q?Trond_Endrest=F8l?= X-Mailer: Apple Mail (2.1085) 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 15:33:21 -0000 On Dec 9, 2013, at 12:15 AM, Trond Endrest=F8l wrote: > On Fri, 6 Dec 2013 11:23-0600, Mark Felder wrote: >=20 >>=20 >>=20 >> On Fri, Dec 6, 2013, at 6:46, Trond Endrest=F8l wrote: >>> Hi, >>>=20 >>> Today I came across "Becoming a ZFS Ninja Part 1"=20 >>> http://www.youtube.com/watch?v=3DtPsV_8k-aVU featuring Ben Rockwood = who=20 >>> stated that ZFS reserves 1/64 of the capacity for COW safe-guarding.=20= >>> Fast forward to 00:49:44. Thus, one should take this fact into = account=20 >>> when planning the storage capacity of your (larger) zpools. >>>=20 >>> Does FreeBSD's ZFS also reserve 1/64 of the capacity for COW? >>>=20 >>> If it's true, then I guess this should be noted in zpool(8) and in = the=20 >>> Handbook. >>>=20 >>=20 >> 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 :-) >=20 > As it turns out, you're in good company, I'm also wrong far too often. I have a zpool that I share between development (/usr/src) and videos = (tivo backups). When it gets over 90% full, I start to see buildworld or = svn operations slow way down... Warner