Date: Mon, 19 Feb 2007 16:25:32 -0500 From: Kris Kennaway <kris@obsecurity.org> To: Volker <volker@vwsoft.com> Cc: freebsd-stable@freebsd.org, Kris Kennaway <kris@obsecurity.org> Subject: Re: getting garbage faster using FreeBSD? Message-ID: <20070219212532.GA43496@xor.obsecurity.org> In-Reply-To: <45DA121E.1040803@vwsoft.com> References: <45D9FD35.6040702@vwsoft.com> <20070219195143.GA42379@xor.obsecurity.org> <45DA121E.1040803@vwsoft.com>
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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
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