From owner-freebsd-questions Sun Sep 1 15:36:50 2002 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9D0AE37B400; Sun, 1 Sep 2002 15:36:47 -0700 (PDT) Received: from smtp.infracaninophile.co.uk (happy-idiot-talk.infracaninophile.co.uk [81.2.69.218]) by mx1.FreeBSD.org (Postfix) with ESMTP id 5E32143E42; Sun, 1 Sep 2002 15:36:46 -0700 (PDT) (envelope-from m.seaman@infracaninophile.co.uk) Received: from happy-idiot-talk.infracaninophile.co.uk ([IPv6:::1]) by smtp.infracaninophile.co.uk (8.12.5/8.12.5) with ESMTP id g81MaiGk013010; Sun, 1 Sep 2002 23:36:44 +0100 (BST) (envelope-from matthew@happy-idiot-talk.infracaninophile.co.uk) Received: (from matthew@localhost) by happy-idiot-talk.infracaninophile.co.uk (8.12.5/8.12.5/Submit) id g81MadqA013009; Sun, 1 Sep 2002 23:36:39 +0100 (BST) Date: Sun, 1 Sep 2002 23:36:39 +0100 From: Matthew Seaman To: Peter Leftwich Cc: "Greg 'groggy' Lehey" , Giorgos Keramidas , FreeBSD LIST Subject: Re: dd if=/dev/zero of=/dev/ad1 Message-ID: <20020901223639.GA12421@happy-idiot-talk.infracaninophi> References: <20020826013322.GD88156@wantadilla.lemis.com> <20020901152742.M37627-100000@earl-grey.cloud9.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020901152742.M37627-100000@earl-grey.cloud9.net> User-Agent: Mutt/1.5.1i Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Sun, Sep 01, 2002 at 03:29:20PM -0400, Peter Leftwich wrote: > On Mon, 26 Aug 2002, Greg 'groggy' Lehey wrote: > > > True. You might want to use a large block size to speed operations if > > > possible (less I/O calls from dd(1) to the kernel, and more freedom to > > > the kernel drivers to arrange in which order data is zeroed). Try at > > > least 32 KB. > > The optimum is the maximum transfer size, currently 128 kB. > > Greg {See complete headers for address and phone numbers} > > What determines that the optimum/maximum transfer size is currently 128 kB? > My HDD and hardware or the most current version of the OS FreeBSD 4.6.2? It's part of the IDE specification: 128k is the maximum IO transfer size. Oh --- the equivalent figure for SCSI discs is 64kB. http://www.freebsd.org/cgi/getmsg.cgi?fetch=2144092+2148744+/usr/local/www/db/text/2002/freebsd-questions/20020811.freebsd-questions Cheers, Matthew -- Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks Savill Way Marlow Tel: +44 1628 476614 Bucks., SL7 1TH UK To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message