From owner-freebsd-stable@FreeBSD.ORG Mon Feb 19 21:25:35 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 85D6B16D890 for ; Mon, 19 Feb 2007 21:25:35 +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 712BC13C478 for ; Mon, 19 Feb 2007 21:25:35 +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 1BFA61A4D82; Mon, 19 Feb 2007 13:25:35 -0800 (PST) Received: by obsecurity.dyndns.org (Postfix, from userid 1000) id 3246C515BC; Mon, 19 Feb 2007 16:25:33 -0500 (EST) Date: Mon, 19 Feb 2007 16:25:32 -0500 From: Kris Kennaway To: Volker Message-ID: <20070219212532.GA43496@xor.obsecurity.org> References: <45D9FD35.6040702@vwsoft.com> <20070219195143.GA42379@xor.obsecurity.org> <45DA121E.1040803@vwsoft.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45DA121E.1040803@vwsoft.com> User-Agent: Mutt/1.4.2.2i Cc: 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: Mon, 19 Feb 2007 21:25:35 -0000 On Mon, Feb 19, 2007 at 10:09:50PM +0100, Volker wrote: > 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. Yes, it could be - you should do some more tests to find out where your bottleneck really is before trying to possibly optimize the wrong thing. > >> Is there any chance to speed up /dev/random? Would a hifn > >> accelerator card help here to get FreeBSD produce garbage faster? > >> > >> As there is medical data on all media I really need garbage > >> (/dev/zero wouldn't be enough for data security as this might get > >> recovered). > > > > Neither would a single pass with /dev/random, but you presumably knew > > this. > > Yes, I know... I would like to run 5 or more passes if it's not that > slow. > > Do you think playing with randoms' sysctl interface might influence > performance? Does /dev/random automatically re-seed from time to > time or is it seeded at boot time only? It re-seeds continuously, see random(4) and/or the yarrow specification. Don't frob the sysctls until you have confirmed that /dev/random is really your problem though. Kris