atom feed3 messages in org.freebsd.freebsd-questionsccd performance limit?
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Hans HuebnerApr 22, 1998 7:27 am 
Vallo KallasteApr 22, 1998 10:07 am 
Greg LeheyApr 23, 1998 7:16 pm 
Subject:ccd performance limit?
From:Hans Huebner (ha@artcom.de)
Date:Apr 22, 1998 7:27:51 am
List:org.freebsd.freebsd-questions

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

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