From owner-freebsd-questions@FreeBSD.ORG Sat Feb 18 14:59:53 2012 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 37714106566C for ; Sat, 18 Feb 2012 14:59:53 +0000 (UTC) (envelope-from freebsd-questions@herveybayaustralia.com.au) Received: from mail.unitedinsong.com.au (mail.unitedinsong.com.au [150.101.178.33]) by mx1.freebsd.org (Postfix) with ESMTP id D268A8FC08 for ; Sat, 18 Feb 2012 14:59:52 +0000 (UTC) Received: from mail.unitedinsong.com.au (bell.herveybayaustralia.com.au [192.168.0.40]) by mail.unitedinsong.com.au (Postfix) with ESMTP id 8CB455C2B for ; Sun, 19 Feb 2012 01:13:18 +1000 (EST) Received: from laptop1.herveybayaustralia.com.au (laptop1.herveybayaustralia.com.au [192.168.0.177]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by mail.unitedinsong.com.au (Postfix) with ESMTPSA id 349385C22 for ; Sun, 19 Feb 2012 01:13:18 +1000 (EST) Message-ID: <4F3FBBC8.3030005@herveybayaustralia.com.au> Date: Sun, 19 Feb 2012 00:55:04 +1000 From: Da Rock User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:7.0.1) Gecko/20111109 Thunderbird/7.0.1 MIME-Version: 1.0 To: freebsd-questions@freebsd.org References: <4F3ECF23.5000706@fisglobal.com> <20120217234623.cf7e169c.freebsd@edvax.de> <3D08D03C85ACFBB1ABCDC5DA@mac-pro.magehandbook.com> <20120218112252.772c878b.freebsd@edvax.de> <4F3F80FD.8070201@herveybayaustralia.com.au> <4F3F8A46.1090908@infracaninophile.co.uk> <4F3F8D39.80907@herveybayaustralia.com.au> <4F3FA9FB.7030203@infracaninophile.co.uk> <4F3FAC17.8000300@herveybayaustralia.com.au> <4F3FB5A0.9020806@infracaninophile.co.uk> In-Reply-To: <4F3FB5A0.9020806@infracaninophile.co.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: /usr/home vs /home X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: freebsd-questions@freebsd.org List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 18 Feb 2012 14:59:53 -0000 On 02/19/12 00:28, Matthew Seaman wrote: > On 18/02/2012 13:48, Da Rock wrote: >> I was thinking along the lines of continuous heavy load of writing (some >> read) rather large files (5G+ would be average - multiple!) - does that >> warrant caching or is it only lots of smaller files? That and lots of >> ~0.5G files (read mostly) is what defines the main load on the system. >> >> I ask because I'm not 100% sure of what the caching is for. I had >> thought it was like the journal log for fast writing to be later written >> to the filesystem itself, but now I think I may be wrong in my >> judgement. It now sounds like a fast access for usual suspects. >> >> Now you see how a terabyte and a half disk space can be used in a matter >> of hours :) > Right. That's a lot more file IO than I anticipated in my previous > answer. For that amount of usage, 8GB would definitely be required and > quite possibly more. Separate devices for ZIL and ARC would be a good > idea. (ZIL is effectively the caching for the write path, ARC for the > read path. That's a gross over-simplification actually, but good enough.) > > The caching is vital -- it's where all the stuff like checking the > parity for a RAIDZn device happens, or the compression/decompression > actions. Yes, it works like file system journalling too. Thanks for the tips Matthew. Now you know why I haven't tackled that hurdle yet :) I'm gunna need some serious hardware...