From mboxrd@z Thu Jan  1 00:00:00 1970
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
In-reply-to: Your message of "Mon, 10 Mar 2008 15:27:47 EDT."
	<881793239e35447fa8c007dc3c084aea@coraid.com>
From: Bakul Shah <bakul+plan9@bitblocks.com>
Date: Mon, 10 Mar 2008 13:55:36 -0700
Message-Id: <20080310205536.75ADA5B59@mail.bitblocks.com>
Subject: Re: [9fans] thoughs about venti+fossil
Topicbox-Message-UUID: 74914740-ead3-11e9-9d60-3106f5b1d025

On Mon, 10 Mar 2008 15:27:47 EDT erik quanstrom <quanstro@coraid.com>  wrote:
> >
> > > brushing off the factor of 2^60 is like brushing off the difference
> > > in weight between a bunch of banannas and the moon.
> >
> > bunch of bananas = ~1kg
> > mass of moon (weight of moon @ earth's sea level) = 7.3477^22 kg
> > 2^60      =    1,152,921,504,606,846,976 = 1.15etc^18
> >
> > Oh oh, you're off by 4 orders of magnitude, I think I hear collisions...
>
> that's cause it's 2^80 not 2^60.  did i mistype?

Nonrecoverable read error rate for disks is typically 1 in
10^14.  While >0.5 probability that two arbitrary blocks hash
to the same SHA1 value is 1 in 2^80.  That is roughly a
factor of 10 Billion.  So we are talking about a bunch of
bananas and less than 1000 Chiquita cargo ships.