From owner-freebsd-stable@FreeBSD.ORG Sat May 14 14:00:44 2005 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id A9AA816A4D0 for ; Sat, 14 May 2005 14:00:44 +0000 (GMT) Received: from wproxy.gmail.com (wproxy.gmail.com [64.233.184.198]) by mx1.FreeBSD.org (Postfix) with ESMTP id 30BF043D6B for ; Sat, 14 May 2005 14:00:44 +0000 (GMT) (envelope-from vohand@gmail.com) Received: by wproxy.gmail.com with SMTP id 69so1139243wri for ; Sat, 14 May 2005 07:00:43 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=Dajz29HWNT1/RXviVsNEMX1LD52PlF3hlAjGCtILr2HN305XOjBi1JFGpmkrrLfWuzEgZmhWZK44phD0WjPo5MVE6b6TZwL2vn9yBV/e4gsAAH1oDjQkDmIPhCxHhdxi1+HU+qo893jsn0dVWquY93LHzsQVePQLGAp/M6aXD2s= Received: by 10.54.133.2 with SMTP id g2mr2312792wrd; Sat, 14 May 2005 07:00:43 -0700 (PDT) Received: by 10.54.97.17 with HTTP; Sat, 14 May 2005 07:00:43 -0700 (PDT) Message-ID: <4200469905051407007484832@mail.gmail.com> Date: Sat, 14 May 2005 18:00:43 +0400 From: Vladimir Dzhivsanoff To: Pawel Jakub Dawidek In-Reply-To: <20050514131648.GB837@darkness.comp.waw.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline References: <20050514093217.C6088E082A@oak.tantieme.ru> <20050514131648.GB837@darkness.comp.waw.pl> cc: freebsd-stable@freebsd.org Subject: Re: gmirror X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: Vladimir Dzhivsanoff List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 May 2005 14:00:44 -0000 On 5/14/05, Pawel Jakub Dawidek wrote: > On Sat, May 14, 2005 at 01:22:05PM +0400, vohand@gmail.com wrote: > +>=20 > +> Hardware: SATA RAID adapter with SiliconImage 3114 chip. 2 SATA HDD. > +> I did gmirror. > +>=20 > +> Run test: > +> 3 parallel tasks "dd if=3D/dev/mirror/gm0 of=3D/dev/null bs=3D1m count= =3D5000" > +>=20 > +> gstat shows summary read speed from mirror about 30-40 mbyte/sec. > +> It is for all balance algorithms: load, round-robin, split > +>=20 > +> While, one "dd if=3D/dev/ad4 of=3D/dev/null bs=3D1m count=3D5000" show= s 50 > mbyte/sec > +>=20 > +> 1. Why it occurs and how fix it ? > +>=20 > +> 2. If in the test instead of three instancies of "dd if=3D/dev/mirror/= gm0 > +> of=3D/dev/null bs=3D1m count=3D5000" run only one,=20 > +> then read speed don`t exceeds read speed from one disk (dd > if=3D/dev/ad4 > +> of=3D/dev/null bs=3D1m count=3D5000) > +> =09a) This is gmirror feature ? > +> =09b) This is hardware feature (SiliconImage 3114 chip) ? >=20 > This is the way RAID1 works. Try to imagine how disk's heads are moving - > there will be no speed-up in sequential reads, this is not RAID0. >=20 > Mirror characteristics are: > - the same speed for sequential reads as for one disk; > - the same speed for sequential/random write as for one disk; =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D > - double speed of one disk for random reads; by what test-suite I can test it ? and what balance algorithm is more proper for random reads ? three parallel tasks of "dd ...." is not good model for random reads ? >=20 > --=20 > Pawel Jakub Dawidek http://www.wheel.pl > pjd@FreeBSD.org http://www.FreeBSD.org > FreeBSD committer Am I Evil? Yes, I Am! >=20 >