From owner-freebsd-questions@FreeBSD.ORG Wed Sep 21 14:40:04 2011 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 184F6106564A for ; Wed, 21 Sep 2011 14:40:04 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: from mail-ey0-f182.google.com (mail-ey0-f182.google.com [209.85.215.182]) by mx1.freebsd.org (Postfix) with ESMTP id 980858FC16 for ; Wed, 21 Sep 2011 14:40:03 +0000 (UTC) Received: by eyg7 with SMTP id 7so1355613eyg.13 for ; Wed, 21 Sep 2011 07:40:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=date:from:to:subject:message-id:in-reply-to:references:x-mailer :mime-version:content-type:content-transfer-encoding; bh=fNA7MpqMu+3t09zAzQjpq0r/l4uSlb8sqiIcwN6fv8E=; b=kcbNYjc4QefHphckBZf5pDteQPTM7yvMhQlVQh+xqm84/jKJO0fCOZZUSYplM1E7yR 1A9/W/tZadmQbMKIHPaSQ6dKs/K3+87O1P6H2qiMTxj2OcNzNfOXlCUi0uCFgiYBAFdd 5/bDDQgTr9UGqs3yNRB+GKd10YLf8G/s4zOos= Received: by 10.216.230.214 with SMTP id j64mr857123weq.64.1316616002293; Wed, 21 Sep 2011 07:40:02 -0700 (PDT) Received: from gumby.homeunix.com (87-194-105-247.bethere.co.uk. [87.194.105.247]) by mx.google.com with ESMTPS id y10sm7138743wbm.14.2011.09.21.07.39.59 (version=SSLv3 cipher=OTHER); Wed, 21 Sep 2011 07:40:00 -0700 (PDT) Date: Wed, 21 Sep 2011 15:39:58 +0100 From: RW To: freebsd-questions@freebsd.org Message-ID: <20110921153958.73c1abf1@gumby.homeunix.com> In-Reply-To: <4E79BF44.206@infracaninophile.co.uk> References: <4E79BF44.206@infracaninophile.co.uk> X-Mailer: Claws Mail 3.7.10 (GTK+ 2.24.6; amd64-portbld-freebsd8.2) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: UFS journal size X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Sep 2011 14:40:04 -0000 On Wed, 21 Sep 2011 11:41:08 +0100 Matthew Seaman wrote: > On 21/09/2011 10:48, Ross wrote: > > My question is: if I have 4 or 8 GB of RAM should I create 8 or even > > 16 GB journals?.. This seems huge especially if the fs size without > > journal is only 10 gigs. Or the recommended minimum is for systems > > low on RAM? > > The 'twice physical RAM' advice is all about achieving maximum > performance on large filesystems with lots of data writes: IIRC the original justification for 2*ram was as a crude rule-of-thumb to avoid panics. I think the idea was that writing the whole ram into one of the two journalling areas was an extreme case. > You might just as well use plain UFS+Softupdates. Softupdates to > provide the meta-data ordering feature, so that if you do crash and > need to fsck the filesystem, there's not going to be any really nasty > stuff to fix. And in 9.x UFS filesystems (even existing ones) will be able to use journalled soft-updates. This should give a fast fsck without the overheads of full data journalling or background fsck. > Plain UFS because a filesystem of that size will take > about as long to fsck as it would to replay all the journalled but > uncommitted updates. FWIW fsck doesn't replay the journal, it just does a quick check for orphaned files and marks the filesystem as clean - uncommitted updates are left for gjournal.