Date: Tue, 20 Feb 2007 13:00:51 -0500 From: Bill Moran <wmoran@collaborativefusion.com> To: Kris Kennaway <kris@obsecurity.org> Cc: Volker <volker@vwsoft.com>, freebsd-stable@freebsd.org Subject: Re: getting garbage faster using FreeBSD? Message-ID: <20070220130051.bfcf6cf2.wmoran@collaborativefusion.com> In-Reply-To: <20070220165012.GB75535@xor.obsecurity.org> References: <45D9FD35.6040702@vwsoft.com> <20070219195143.GA42379@xor.obsecurity.org> <45DA121E.1040803@vwsoft.com> <20070220091238.c04cfceb.wmoran@collaborativefusion.com> <20070220165012.GB75535@xor.obsecurity.org>
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In response to Kris Kennaway <kris@obsecurity.org>: > On Tue, Feb 20, 2007 at 09:12:38AM -0500, Bill Moran wrote: > > In response to Volker <volker@vwsoft.com>: > > > > > 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. Interesting ... I could swear I recently had a problem with /dev/random blocking on a 6.X system ... I'll have to take another look. -- Bill Moran Collaborative Fusion Inc.
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