From owner-freebsd-hackers@FreeBSD.ORG Mon Sep 29 02:13:07 2008 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 445521065687 for ; Mon, 29 Sep 2008 02:13:07 +0000 (UTC) (envelope-from fbsd06+2H=66b76f71@mlists.homeunix.com) Received: from fallback-in1.mxes.net (fallback-out1.mxes.net [216.86.168.190]) by mx1.freebsd.org (Postfix) with ESMTP id 1703B8FC0A for ; Mon, 29 Sep 2008 02:13:07 +0000 (UTC) (envelope-from fbsd06+2H=66b76f71@mlists.homeunix.com) Received: from mxout-03.mxes.net (mxout-03.mxes.net [216.86.168.178]) by fallback-in1.mxes.net (Postfix) with ESMTP id CE280163F6B for ; Sun, 28 Sep 2008 21:56:40 -0400 (EDT) Received: from gumby.homeunix.com. (unknown [87.81.140.128]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.mxes.net (Postfix) with ESMTP id E0AF123E49A; Sun, 28 Sep 2008 21:56:38 -0400 (EDT) Date: Mon, 29 Sep 2008 02:56:36 +0100 From: RW To: "Michael Schuh" Message-ID: <20080929025636.781ed1ff@gumby.homeunix.com.> In-Reply-To: <1dbad3150809261115h379a611aweb20e47124e254d4@mail.gmail.com> References: <1dbad3150809261115h379a611aweb20e47124e254d4@mail.gmail.com> X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.11; i386-portbld-freebsd7.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: freebsd-hackers@freebsd.org Subject: Re: experimantal question about md's 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: Mon, 29 Sep 2008 02:13:07 -0000 On Fri, 26 Sep 2008 20:15:43 +0200 "Michael Schuh" wrote: > Let us say i have a Machine with 8 CPUs and a lot of RAM. > An i need a very high perfomance Storage for holding data. > > My idea was to setup a raid1(0) with virtual disk images. > Created with mdconfig. > > My idea was to create minimum 2 md-diskimages, > these are located > fisrt one on the harddisk as type vnode > second one as exact copy totally in the memory as type malloc > > For now the man-page mentoid me to not to do so, while large disks in > RAM cause panics, and i know panics come surely > > Is the above scenario possible without panics? You could use swap-backed devices. They are very similar, in both cases you are writing into ram backed by swap. I doubt it will work, I think raid works at the speed of the slower device. You need to be careful how you benchmark it. Your raid array will have the unfair advantage of starting with preloaded data.