From owner-freebsd-questions Wed Apr 22 07:28:17 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id HAA21775 for freebsd-questions-outgoing; Wed, 22 Apr 1998 07:28:17 -0700 (PDT) (envelope-from owner-freebsd-questions@FreeBSD.ORG) Received: from mail.artcom.de (tui.artcom.de [192.76.129.2]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id OAA21766 for ; Wed, 22 Apr 1998 14:28:12 GMT (envelope-from hans@artcom.de) Received: from transrapid.artcom.de by mail.artcom.de with smtp id m0yS0VQ-000008C; Wed, 22 Apr 1998 16:28:12 +0200 (MEST) Date: Wed, 22 Apr 1998 16:28:12 +0200 (MEST) From: Hans Huebner To: freebsd-questions@FreeBSD.ORG Subject: ccd performance limit? Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG 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