From owner-freebsd-questions@FreeBSD.ORG Fri Jul 25 10:01:42 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 93520106567D for ; Fri, 25 Jul 2008 10:01:42 +0000 (UTC) (envelope-from nicodache@gmail.com) Received: from rv-out-0506.google.com (rv-out-0506.google.com [209.85.198.239]) by mx1.freebsd.org (Postfix) with ESMTP id 5A9988FC19 for ; Fri, 25 Jul 2008 10:01:42 +0000 (UTC) (envelope-from nicodache@gmail.com) Received: by rv-out-0506.google.com with SMTP id b25so4021644rvf.43 for ; Fri, 25 Jul 2008 03:01:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=Rh2qXwbQ+WeUxveBAnoeyXYFqg2+nJEsguX9ek6rkZo=; b=QSaZo7JLEwgHhv2BvrZDmsvlI8cf4s2yylP+ul5Tc+bDNhJhQhbtsVwLFZ2WMe/j7k 5hRwyAWuqmybuC7/zuV/9JXPTZlz1TyjlMHopzmAhK8Ga5fACu6Op9RKgGKTjRRP10Rd 4HcASF+VfbUuug+2e6PG5NoQQawDqfE5K28rU= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=j+vN8dJ4yYYb3IW7urf/qc3xvtRilDeT3jFQyesnPnPTY68W2uRmR1wzlQqrgzapot AAj5FpZllsWFibeBjAv2NBoIV0htp3WbfSMs8Ol0ITSbclF0vWw3Oc67peAJODe7vYRL 2gNW/3JbekdvFiFazNuWiFGYSt/ubYqRPQGHw= Received: by 10.141.136.19 with SMTP id o19mr769412rvn.281.1216980101662; Fri, 25 Jul 2008 03:01:41 -0700 (PDT) Received: by 10.141.19.11 with HTTP; Fri, 25 Jul 2008 03:01:41 -0700 (PDT) Message-ID: <82029aed0807250301h638f6243u5c435dcfaaac7d9f@mail.gmail.com> Date: Fri, 25 Jul 2008 12:01:41 +0200 From: nicodache To: freebsd-questions@freebsd.org In-Reply-To: <20080725114402.G5386@wojtek.tensor.gdynia.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080725114402.G5386@wojtek.tensor.gdynia.pl> Subject: Re: graid3 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Jul 2008 10:01:42 -0000 Hello, 1. I don't see such a thing on the weblink you gave (acnc) In my opinion, this rule is pure nonsense, as raid 3 just use a separate drive to store stripe parity. You just need at least 3 drives, one for parity, 2 for data. you can do raid 3 with how many drives you want. 2. because the raid controler/software thing can reconstruct the data with only n-1 of the n drives in the array. in random IO this can be quite usefull, while in sequential read, the parity drive is not that much of use. On Fri, Jul 25, 2008 at 11:46 AM, Wojciech Puchar wrote: > i read the graid3 manual and http://www.acnc.com/04_01_03.html to make sure > i know what's RAID3 and i don't understand few things. > > 1) > > "The number of components must be equal to 3, 5, 9, 17, etc. > (2^n + 1)." > > why it can't be say 5 disks+parity? > > 2) "-r Use parity component for reading in round-robin fashion. > "Without this option the parity component is not used at > all for reading operations when the device is in a complete state. > With this option specified random I/O read operations are even 40% faster > , but sequential reads are slower. One cannot use this option if the -w > option is also specified." > > > how parity disk could speed up random I/O? > > > is there any description of how graid3 actually works? > > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" >