From owner-freebsd-hardware Tue Mar 12 00:51:45 1996 Return-Path: owner-hardware Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id AAA15900 for hardware-outgoing; Tue, 12 Mar 1996 00:51:45 -0800 (PST) Received: from irz301.inf.tu-dresden.de (irz301.inf.tu-dresden.de [141.76.1.11]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id AAA15820 Tue, 12 Mar 1996 00:51:11 -0800 (PST) Received: from sax.sax.de by irz301.inf.tu-dresden.de (8.6.12/8.6.12-s1) with ESMTP id JAA00426; Tue, 12 Mar 1996 09:50:41 +0100 Received: by sax.sax.de (8.6.11/8.6.12-s1) with UUCP id JAA02596; Tue, 12 Mar 1996 09:50:40 +0100 Received: (from j@localhost) by uriah.heep.sax.de (8.7.4/8.6.9) id JAA04130; Tue, 12 Mar 1996 09:42:29 +0100 (MET) From: J Wunsch Message-Id: <199603120842.JAA04130@uriah.heep.sax.de> Subject: Re: Slow Toshiba 6.7X cdrom drive. To: rgrimes@GndRsh.aac.dev.com (Rodney W. Grimes) Date: Tue, 12 Mar 1996 09:42:29 +0100 (MET) Cc: joerg_wunsch@uriah.heep.sax.de, fcawth@jjarray.umd.edu, freebsd-scsi@FreeBSD.org, freebsd-hardware@FreeBSD.org Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) In-Reply-To: <199603120239.SAA13266@GndRsh.aac.dev.com> from "Rodney W. Grimes" at Mar 11, 96 06:39:50 pm X-Phone: +49-351-2012 669 X-Mailer: ELM [version 2.4 PL24 ME8a] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-hardware@FreeBSD.org X-Loop: FreeBSD.org Precedence: bulk As Rodney W. Grimes wrote: > Try the 3 following dd commands, I found that xfer rates on multispin > cdrom drives is heavily block size dependent. > > dd if=/dev/rcd0a of=/dev/null bs=512 > dd if=/dev/rcd0a of=/dev/null bs=2048 > dd if=/dev/rcd0a of=/dev/null bs=8192 > > Many drives will due there highest rate with the 8K I/O, a few others > seem to like the 2K I/O. The optimum is 8 K blocks (~ 500 KB/s). When enlarging the blocksize again (500 K, dunno how the driver does slice this request), it drops to the aforementioned 300 KB/s. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)