From owner-freebsd-hackers Sun Aug 30 08:03:50 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id IAA27548 for freebsd-hackers-outgoing; Sun, 30 Aug 1998 08:03:50 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from mail.camalott.com (mail.camalott.com [208.203.140.2]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id IAA27542 for ; Sun, 30 Aug 1998 08:03:48 -0700 (PDT) (envelope-from joelh@gnu.org) Received: from detlev.UUCP (tex-80.camalott.com [208.229.74.80]) by mail.camalott.com (8.8.7/8.8.5) with ESMTP id KAA08844; Sun, 30 Aug 1998 10:04:26 -0500 Received: (from joelh@localhost) by detlev.UUCP (8.9.1/8.9.1) id KAA07242; Sun, 30 Aug 1998 10:02:34 -0500 (CDT) (envelope-from joelh) Date: Sun, 30 Aug 1998 10:02:34 -0500 (CDT) Message-Id: <199808301502.KAA07242@detlev.UUCP> To: mike@smith.net.au CC: avalon@coombs.anu.edu.au, hackers@FreeBSD.ORG In-reply-to: <199808292159.VAA10620@word.smith.net.au> (message from Mike Smith on Sat, 29 Aug 1998 21:59:08 +0000) Subject: Re: duplicating cd's with dd. From: Joel Ray Holveck Reply-to: joelh@gnu.org References: <199808292159.VAA10620@word.smith.net.au> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >> does anyone know if there are "preferred" parameters for using dd to >> copy cd's with ? > You can improve performance slightly with a larger block size (fewer > syscalls), but that's about it. I use 64K as an arbitrary figure; it > seems to run about as fast as the drive will go. I wrote a small script that tests each blocksize (with the laser off), and plots the number of blocks transferred before a buffer underrun, and the BPS rate. Since this is a slow system (Am486DX/4-100, AHA-1542, CDD-2600), then the timing is quite critical to me, and most block sizes would cause an underrun. I got a pretty clear pattern, indicating the optimal blocksize as 32k. Best, joelh -- Joel Ray Holveck - joelh@gnu.org - http://www.wp.com/piquan Fourth law of programming: Anything that can go wrong wi sendmail: segmentation violation - core dumped To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message