From owner-freebsd-current@FreeBSD.ORG Sun Oct 31 23:37:16 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 87D9916A4CE for ; Sun, 31 Oct 2004 23:37:16 +0000 (GMT) Received: from vhost109.his.com (vhost109.his.com [216.194.225.101]) by mx1.FreeBSD.org (Postfix) with ESMTP id 14F3E43D39 for ; Sun, 31 Oct 2004 23:37:16 +0000 (GMT) (envelope-from brad@stop.mail-abuse.org) Received: from [10.0.1.3] (localhost.his.com [127.0.0.1]) by vhost109.his.com (8.12.11/8.12.3) with ESMTP id i9VNawWH087727; Sun, 31 Oct 2004 18:37:14 -0500 (EST) (envelope-from brad@stop.mail-abuse.org) Mime-Version: 1.0 X-Sender: bs663385@127.0.0.1 Message-Id: In-Reply-To: <002401c4bf9c$c4fee8e0$0201000a@riker> References: <002401c4bf9c$c4fee8e0$0201000a@riker> Date: Mon, 1 Nov 2004 00:26:57 +0100 To: From: Brad Knowles Content-Type: text/plain; charset="us-ascii" ; format="flowed" cc: freebsd-current@freebsd.org Subject: Re: Gvinum RAID5 performance X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 31 Oct 2004 23:37:16 -0000 At 9:55 AM +1100 2004-11-01, wrote: > Now, running a dd from a plex gives me less performance than running a > dd from one of the subdisks, even though the array is not running in > degraded mode. Right. This is RAID-5. It is used for reliability, not performance. The entire stripe has to be read at once and written at once, for any operation involving that stripe. If you want maximum performance, try RAID 1+0 (make sure to stripe the mirrors and not mirror the stripes). > On a final note, I'd like to implement the ability to grow RAID5 plexes > - any suggestions on where to start? This is a more complex issue than you realize. If you want to contribute code to perform this operation, I'm sure that the project would be more than happy to receive them in consideration for inclusion in the gvinum code. -- Brad Knowles, "Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety." -- Benjamin Franklin (1706-1790), reply of the Pennsylvania Assembly to the Governor, November 11, 1755 SAGE member since 1995. See for more info.