Date: Wed, 22 Apr 1998 16:28:12 +0200 (MEST) From: Hans Huebner <hans@artcom.de> To: freebsd-questions@FreeBSD.ORG Subject: ccd performance limit? Message-ID: <Pine.BSF.3.96.980422161855.6711A-100000@transrapid.artcom.de>
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Hello there, I'm currently experimenting with the ccd driver to speed up a particular file system. I'm using an NCR wide SCSI controller and four IBM DCHS09X disk drives. The drives are able to transfer 7-9 MB/second when using large block reads from the raw device. When I measure the performance for all four drives at once, I still get a aggregated transfer rate of around 28 MB per second. When I set up a ccd device with the four disks, I am unable to read more than 14-15 MB per second from the stripe set. I tried various different interleave factors (and found that 36 seems to be the optimum value). Does anyone have an explanation for this limitation? Thanks, -Hans To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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