Date: Tue, 12 Mar 1996 01:48:34 -1000 From: richard@pegasus.com (Richard Foulk) To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch), rgrimes@gndrsh.aac.dev.com (Rodney W. Grimes) Cc: fcawth@jjarray.umd.edu, freebsd-scsi@FreeBSD.org, freebsd-hardware@FreeBSD.org Subject: Re: Slow Toshiba 6.7X cdrom drive. Message-ID: <199603121148.BAA01250@pegasus.com> In-Reply-To: J Wunsch <j@uriah.heep.sax.de> "Re: Slow Toshiba 6.7X cdrom drive." (Mar 12, 9:42am)
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} > 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. } Hmm. Maybe the driver should be tunable.
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