Date: Tue, 12 Mar 1996 09:42:29 +0100 (MET) From: J Wunsch <j@uriah.heep.sax.de> To: rgrimes@GndRsh.aac.dev.com (Rodney W. Grimes) Cc: joerg_wunsch@uriah.heep.sax.de, fcawth@jjarray.umd.edu, freebsd-scsi@FreeBSD.org, freebsd-hardware@FreeBSD.org Subject: Re: Slow Toshiba 6.7X cdrom drive. Message-ID: <199603120842.JAA04130@uriah.heep.sax.de> In-Reply-To: <199603120239.SAA13266@GndRsh.aac.dev.com> from "Rodney W. Grimes" at Mar 11, 96 06:39:50 pm
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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. ;-)
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