From owner-freebsd-hackers@FreeBSD.ORG Sun Jun 25 10:24:10 2006 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E413F16A402 for ; Sun, 25 Jun 2006 10:24:10 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [209.31.154.42]) by mx1.FreeBSD.org (Postfix) with ESMTP id 78D5043D4C for ; Sun, 25 Jun 2006 10:24:10 +0000 (GMT) (envelope-from rwatson@FreeBSD.org) Received: from fledge.watson.org (fledge.watson.org [209.31.154.41]) by cyrus.watson.org (Postfix) with ESMTP id 20B4F46C6E; Sun, 25 Jun 2006 06:24:10 -0400 (EDT) Date: Sun, 25 Jun 2006 11:24:10 +0100 (BST) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: Mike Meyer In-Reply-To: <17565.37706.966913.737964@bhuda.mired.org> Message-ID: <20060625111920.H8526@fledge.watson.org> References: <449D8616.5040306@tamara-b.org> <17565.37706.966913.737964@bhuda.mired.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-hackers@freebsd.org, bob@tamara-b.org Subject: Re: A New FreeBSD Server X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 25 Jun 2006 10:24:11 -0000 On Sat, 24 Jun 2006, Mike Meyer wrote: >> Swap drive, should probably be a piece of one of the 17GB drives (NO RAID) >> the Box has 500MB ram...... > > Why not RAID your swap? The extra reliability might not be worth very much, > but the extra performance couldn't hurt - unless you don't plan on swapping > at all. This is enough of a win that the swap subsystem will interleave swap > usage across multiple drives, a facility that predates RAID. If you just > split your swap across multiple drives, you get RAID0 behavior from swap. On my boxes, I always put swap on RAID, for two reasons: (1) When swapping, performance does matter, so having the extra throughput and reduced latency helps quite a bit under load. This is especially important if you use a swap-backed temporary file system for /tmp. (2) System reliability depends on swap reliability. Specifically, if your init process, or X server, etc loses its memory because your swap disk dies, that's really bad for reliability. Similar arguments apply to system boot disks, which are left out of RAIDs by some administrators. Data corruption in swap or system programs and data can result in overall system failures, and the possibility of data corruption due to misbehaving apps, etc. I always stick all swap and file systems on RAID for critical systems in order to avoid the cost and risks of recovering from a non-RAID failure. Robert N M Watson Computer Laboratory University of Cambridge