Date: Fri, 24 Apr 1998 10:17:16 +0800 From: Greg Lehey <grog@lemis.com> To: Vallo Kallaste <vallo@matti.ee>, freebsd-questions@FreeBSD.ORG Subject: Re: ccd performance limit? Message-ID: <19980424101716.53779@papillon.lemis.com> In-Reply-To: <Pine.GSO.3.96.980422200249.26285A-100000@solaris>; from Vallo Kallaste on Wed, Apr 22, 1998 at 08:08:16PM %2B0300 References: <Pine.BSF.3.96.980422161855.6711A-100000@transrapid.artcom.de> <Pine.GSO.3.96.980422200249.26285A-100000@solaris>
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On Wed, 22 April 1998 at 20:08:16 +0300, Vallo Kallaste wrote: > > On Wed, 22 Apr 1998, Hans Huebner wrote: > >> 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). > > I'm also experimenting with ccd at this time and also get only 14-15 MB/s. > I have two Quantum Viking disks and tried different interleave factors, > too. Looks like almost same problem :( The obvious question is: how are you using the stripe set? How are you measuring the throughput? ccd has a certain overhead, of course, but part of its performance increase is due to the ability to server multiple requests in parallel. If you measure only a single requester, you will get results which may not have much significance in practice. If you are measuring multiple access, I'd be interested in knowing how you measure the throughput. I'm currently writing a replacement for ccd. If you're interested, you can test it. I'm not guaranteeing higher throughput, but I'd be interested in comparing it on high-performance disks (I'm developing on the oldest disks I can find, so that I can pinpoint performance problems). Greg To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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