From owner-freebsd-questions Tue Feb 25 15:47:36 2003 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 03A8037B401 for ; Tue, 25 Feb 2003 15:47:35 -0800 (PST) Received: from ra.dweebsoft.com (ra.dweebsoft.com [209.237.40.34]) by mx1.FreeBSD.org (Postfix) with ESMTP id 767DA43F3F for ; Tue, 25 Feb 2003 15:47:34 -0800 (PST) (envelope-from daxbert_news@dweebsoft.com) Received: from ra.dweebsoft.com (localhost [127.0.0.1]) by ra.dweebsoft.com (8.12.6/8.12.6) with ESMTP id h1PNlYs4071891; Tue, 25 Feb 2003 15:47:34 -0800 (PST) (envelope-from daxbert_news@dweebsoft.com) Received: (from http@localhost) by ra.dweebsoft.com (8.12.6/8.12.3/Submit) id h1PNlYIB071890; Tue, 25 Feb 2003 15:47:34 -0800 (PST) X-Authentication-Warning: ra.dweebsoft.com: http set sender to daxbert_news@dweebsoft.com using -f Received: from 64.81.58.36 ( [64.81.58.36]) as user daxbert@localhost by ra.dweebsoft.com with HTTP; Tue, 25 Feb 2003 15:47:34 -0800 Message-ID: <1046216854.3e5c00960e433@ra.dweebsoft.com> Date: Tue, 25 Feb 2003 15:47:34 -0800 From: Daxbert To: Christian Weisgerber Cc: "" Subject: Re: dump: skewed I/O, why? MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit User-Agent: Internet Messaging Program (IMP) 3.1 X-Originating-IP: 64.81.58.36 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Quoting Christian Weisgerber : > During a dump(8) of a filesystem on da0 to a holding file on da1, > with nothing else going on, iostat(8) reports figures such as these: > > da0 da1 cd0 cd1 > KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s > 64.00 148 9.28 64.00 24 1.52 0.00 0 0.00 0.00 0 0.00 > 64.00 138 8.61 61.67 24 1.47 0.00 0 0.00 0.00 0 0.00 > > Why is the I/O ratio so skewed towards reading? > > And yes, this uses dump's recently introduced -C cache option. It might be helpful to know what argument you're passing to dump and how you are redirecting the output. I normally redirect the output to a compression utility and then to disk... so, for me what you're seeing is normal. However, I gather from your surprise that you're not using a compression utility? --daxbert To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message