From owner-freebsd-current@FreeBSD.ORG Sat Nov 6 23:23:23 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 56FAC16A4CE; Sat, 6 Nov 2004 23:23:23 +0000 (GMT) Received: from blackwater.lemis.com (wantadilla.lemis.com [192.109.197.135]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3056043D3F; Sat, 6 Nov 2004 23:23:22 +0000 (GMT) (envelope-from grog@lemis.com) Received: by blackwater.lemis.com (Postfix, from userid 1004) id 2C6D185651; Sun, 7 Nov 2004 09:53:20 +1030 (CST) Date: Sun, 7 Nov 2004 09:53:20 +1030 From: Greg 'groggy' Lehey To: Lukas Ertl Message-ID: <20041106232320.GI24507@wantadilla.lemis.com> References: <002401c4bf9c$c4fee8e0$0201000a@riker> <20041031235355.R1732@korben.prv.univie.ac.at> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="Op27XXJsWz80g3oF" Content-Disposition: inline In-Reply-To: <20041031235355.R1732@korben.prv.univie.ac.at> User-Agent: Mutt/1.4.2.1i Organization: The FreeBSD Project Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-418-838-708 WWW-Home-Page: http://www.FreeBSD.org/ X-PGP-Fingerprint: 9A1B 8202 BCCE B846 F92F 09AC 22E6 F290 507A 4223 cc: freebsd@newmillennium.net.au 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: Sat, 06 Nov 2004 23:23:23 -0000 --Op27XXJsWz80g3oF Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Sunday, 31 October 2004 at 23:56:17 +0100, Lukas Ertl wrote: > On Mon, 1 Nov 2004 freebsd@newmillennium.net.au 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. > > I'd consider this normal behaviour, since you have to go through the > offset calculation. The offset calculations should run at several orders of magnitude faster than the disk transfers. If reading a plex is slower than reading the subdisk, I can see two reasons: 1. Too small a stripe size. If you (our anonymous user, who was using a single dd process) have to perform multiple transfers for a single request, the results will be slower. 2. There may be some overhead in GEOM that slows things down. If this is the case, something should be done about it. I'm pretty sure that the old Vinum would not show this kind of behaviour if (1) doesn't apply. Greg -- See complete headers for address and phone numbers. --Op27XXJsWz80g3oF Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (FreeBSD) iD8DBQFBjVzoIubykFB6QiMRAgs8AJ9inj+zVJ58hfQxA1H7fTNmgCbsewCfTsx8 VJr1anV4+I4OjffedirmyQY= =HNXK -----END PGP SIGNATURE----- --Op27XXJsWz80g3oF--