From owner-freebsd-stable@FreeBSD.ORG Tue Feb 20 16:50:15 2007 Return-Path: X-Original-To: freebsd-stable@freebsd.org Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 7D57116A475 for ; Tue, 20 Feb 2007 16:50:15 +0000 (UTC) (envelope-from kris@obsecurity.org) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.freebsd.org (Postfix) with ESMTP id 6CAFC13C441 for ; Tue, 20 Feb 2007 16:50:15 +0000 (UTC) (envelope-from kris@obsecurity.org) Received: from obsecurity.dyndns.org (elvis.mu.org [192.203.228.196]) by elvis.mu.org (Postfix) with ESMTP id 511141A4D8E; Tue, 20 Feb 2007 08:50:15 -0800 (PST) Received: by obsecurity.dyndns.org (Postfix, from userid 1000) id D451D514EA; Tue, 20 Feb 2007 11:50:12 -0500 (EST) Date: Tue, 20 Feb 2007 11:50:12 -0500 From: Kris Kennaway To: Bill Moran Message-ID: <20070220165012.GB75535@xor.obsecurity.org> References: <45D9FD35.6040702@vwsoft.com> <20070219195143.GA42379@xor.obsecurity.org> <45DA121E.1040803@vwsoft.com> <20070220091238.c04cfceb.wmoran@collaborativefusion.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070220091238.c04cfceb.wmoran@collaborativefusion.com> User-Agent: Mutt/1.4.2.2i Cc: Volker , freebsd-stable@freebsd.org, Kris Kennaway Subject: Re: getting garbage faster using FreeBSD? X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Feb 2007 16:50:15 -0000 On Tue, Feb 20, 2007 at 09:12:38AM -0500, Bill Moran wrote: > In response to Volker : > > > On 02/19/07 20:51, Kris Kennaway wrote: > > > On Mon, Feb 19, 2007 at 08:40:37PM +0100, Volker wrote: > > >> The tape sits there since 48 hours writing a block of data every > > >> other minute and still didn't fill up the tape completely. The > > >> system this is running on is a P-4 3GHz machine using FreeSBIE 2.0 > > >> (6.2-RELEASE based). > > >> > > >> I suspect this to be a slow /dev/random. > > > > > > This sounds odd to me, I get 18-20MB/sec sustained read performance > > > from /dev/random on this 2GHz system, which is probably faster than > > > your tape write speed. > > > > Hmm, so this might be the tape drive(r)? I'll check this out as soon > > as I'm going to write to hard disk. > > > > I'm going to make some tests with /dev/random to get the real speed. > > Are you actually using /dev/random and not /dev/urandom? > > /dev/random is "military grade" random data. It will block if it feels > that it hasn't gathered enough entropy to satisfy your request. It will > never provide random data at any reasonable speed, but it will provide > high-quality random data. > > If you need lost of random data, use /dev/urandom, which provides data > that _may_ be predictable under some circumstances, but will provide > it at a decent rate of speed. Not true in a post 4.x world, they are symlinks and both "military grade" with non-blocking semantics. Kris