From owner-freebsd-questions@FreeBSD.ORG Thu Mar 31 02:46:15 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 6E4E31065673 for ; Thu, 31 Mar 2011 02:46:15 +0000 (UTC) (envelope-from amvandemore@gmail.com) Received: from mail-fx0-f54.google.com (mail-fx0-f54.google.com [209.85.161.54]) by mx1.freebsd.org (Postfix) with ESMTP id 0035E8FC15 for ; Thu, 31 Mar 2011 02:46:14 +0000 (UTC) Received: by fxm11 with SMTP id 11so1984660fxm.13 for ; Wed, 30 Mar 2011 19:46:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=0/9pCZF0ahz+JbXWjWxOOS5QRSaOwWoOg214PsmJFDU=; b=aeGCHcProw9BRXNznO/xXI4Um2NNDd64LwtfyVY9IxyErNPxCKWN2fv7vNmIsJpQTo D4H5Co+Pepe5b9CpYA0B71mtN40Wmj/zG/XonJ/tatX2N5YQjVFA29CfsdhfhxkiInKS oCFUK8VpX3Ggo+/0r74Ga7ZwOLLlBNEdZe+wM= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=eHTcsqJ+aQtoECkmYxqA4jh0WBYx4govyV9qmuVJoXQ0BWCcfbpkvgmVNXDb8TrnE5 R2H6KnqR1G8PMLvOlDil+GzTfU4tvznmkft8B59L8XbX76pxvTMmc5EWCU3e9YPw9PF9 dmRmMWfEl/ZabqnLLJ46hYWcoleONPH5PoPn4= MIME-Version: 1.0 Received: by 10.223.102.129 with SMTP id g1mr747238fao.3.1301539574064; Wed, 30 Mar 2011 19:46:14 -0700 (PDT) Received: by 10.223.101.208 with HTTP; Wed, 30 Mar 2011 19:46:13 -0700 (PDT) In-Reply-To: References: Date: Wed, 30 Mar 2011 21:46:13 -0500 Message-ID: From: Adam Vande More To: Luke Dean Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-questions@freebsd.org Subject: Re: kern.geom.journal.stats.low_mem refers to what? 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: Thu, 31 Mar 2011 02:46:15 -0000 On Wed, Mar 30, 2011 at 9:07 PM, Luke Dean wrote: > > The Handbook says 1GB is good enough most of the time, but it also says >> that 3x the amount of physical memory is a good size as well. I compromised >> between the two and made an 8GB journal for this system that has ~4GB of >> memory. >> > > I've never understood why that article states that calculation. The amount of RAM a system has little to do with what gjournal needs. That formula will in most cases allocate far more journal space than is really necessary. Disk speed and latency are far more important factors. Back when I was using gjournal, I used a 2GB journal on 7200rpm and was never able to panic the system unlike with a 1 GB journal but that was with all other settings at default. Allocating more to gjournal cache would increase the need for space so perhaps it's good you've made such a large one. As you've discovered, gjournal's performance isn't so great when large files are involved. It still helps on multi-threaded access but those big sequential operations destroy most the other optimizations in place. You might want to consider placing your journal on an SSD. -- Adam Vande More