From owner-freebsd-questions@FreeBSD.ORG Tue Mar 27 17:07:27 2007 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 2173316A400 for ; Tue, 27 Mar 2007 17:07:27 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from mail-out3.apple.com (mail-out3.apple.com [17.254.13.22]) by mx1.freebsd.org (Postfix) with ESMTP id 09C5313C4C2 for ; Tue, 27 Mar 2007 17:07:26 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from relay6.apple.com (a17-128-113-36.apple.com [17.128.113.36]) by mail-out3.apple.com (8.13.8/8.13.8) with ESMTP id l2RH7QoM006741; Tue, 27 Mar 2007 10:07:26 -0700 (PDT) Received: from relay6.apple.com (unknown [127.0.0.1]) by relay6.apple.com (Symantec Mail Security) with ESMTP id 95B10100D9; Tue, 27 Mar 2007 10:07:26 -0700 (PDT) X-AuditID: 11807124-ad683bb000001b9e-24-46094f4e824e Received: from [17.214.13.96] (cswiger1.apple.com [17.214.13.96]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by relay6.apple.com (Apple SCV relay) with ESMTP id 7AF6E100CD; Tue, 27 Mar 2007 10:07:26 -0700 (PDT) In-Reply-To: References: Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: Content-Transfer-Encoding: 7bit From: Chuck Swiger Date: Tue, 27 Mar 2007 10:07:25 -0700 To: "Marc G. Fournier" X-Mailer: Apple Mail (2.752.2) X-Brightmail-Tracker: AAAAAA== Cc: freebsd-questions@freebsd.org Subject: Re: mdconfig device no faster then direct disk ... X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 27 Mar 2007 17:07:27 -0000 On Mar 26, 2007, at 6:55 PM, Marc G. Fournier wrote: > 45 processes: 1 running, 44 sleeping > CPU states: 0.0% user, 0.0% nice, 0.4% system, 0.4% interrupt, > 99.2% idle > Mem: 35M Active, 285M Inact, 271M Wired, 44K Cache, 111M Buf, 402M > Free > Swap: 2007M Total, 2007M Free > > I just did: > > mdconfig -a -t malloc -s 200m -o reserve > newfs /dev/md0 > > Now, my understanding, this builds a file system 'in core', vs on > the disk ... > with memory being faster then disk, I would have assumed that read/ > write > performance would have been better, but, using iozone, I'm not > finding enough > of a difference in performance to understand why I'd want to use a > memory file > system: In order to do useful disk benchmarks, you've got to perform I/O on large enough files that they don't fit into RAM. If you've got 400- odd MB completely unused according to top, you'd really like to use at least 1-2 GB worth of file data. Of course, trying to do I/O tests on a RAM disk means that you want the data to fit into RAM without swapping, which then means that trying to do identical testing between disk and RAMdisk doesn't really work too well. -- -Chuck