From owner-freebsd-questions@FreeBSD.ORG Fri Jun 13 14:01:32 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 72588106573C for ; Fri, 13 Jun 2008 14:01:32 +0000 (UTC) (envelope-from dkelly@Grumpy.DynDNS.org) Received: from smtp.knology.net (smtp.knology.net [24.214.63.101]) by mx1.freebsd.org (Postfix) with ESMTP id EC61B8FC0A for ; Fri, 13 Jun 2008 14:01:31 +0000 (UTC) (envelope-from dkelly@Grumpy.DynDNS.org) Received: (qmail 27249 invoked by uid 0); 13 Jun 2008 14:01:30 -0000 Received: from unknown (HELO Grumpy.DynDNS.org) (216.186.148.249) by smtp7.knology.net with SMTP; 13 Jun 2008 14:01:30 -0000 Received: by Grumpy.DynDNS.org (Postfix, from userid 928) id 29E0928429; Fri, 13 Jun 2008 09:01:30 -0500 (CDT) Date: Fri, 13 Jun 2008 09:01:30 -0500 From: David Kelly To: Wojciech Puchar Message-ID: <20080613140130.GA8616@Grumpy.DynDNS.org> References: <200806121521.16237.kirk@strauser.com> <20080613090714.K4713@wojtek.tensor.gdynia.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080613090714.K4713@wojtek.tensor.gdynia.pl> User-Agent: Mutt/1.4.2.3i Cc: FreeBSD Questions , freebsd-questions@freebsd.org Subject: Re: Stripe sizes with gstripe 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, 13 Jun 2008 14:01:32 -0000 On Fri, Jun 13, 2008 at 09:08:48AM +0200, Wojciech Puchar wrote: > >>Does gstripe read an entire stripe at a time? If so, why do that instead > >>of > >>just reading a few requested blocks? If not, then is there any advantage > >>to large stripes? > > > >Apparently it won't read anything larger than your stripe size which > >defaults to a miserable 4k. > > > depending from what's needed, but unless i need just huge linear transfer, > i set stripe size to something huge, like 256MB. > > then single read is rarely split on 2 disks, while multiple reads have > good chances to touch different drives Come to think of it I didn't try setting the stripe size larger than the ATA max transaction size of 128k. Still, I don't understand what is going on when I use md5(1) on a gigabyte file hosted on a gstripe partition with 128k stripes that "systat -v" reports transactions are usually between 42k and 43k each? On a non-striped filesystem the same operation runs 126k to 127k transfers. Transfer bandwidth seems to be limited by the number of transactions per second more than the size of the transaction. -- David Kelly N4HHE, dkelly@HiWAAY.net ======================================================================== Whom computers would destroy, they must first drive mad.