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 "Thu, 05 Jan 2012 13:01:52 EST."
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References: <20120105124852.GA940@polynum.com>
	<20120105144810.182add7c@wks-ddc.exosec.local>
	<20120105151518.GB435@polynum.com>
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	<20120105163907.GA761@polynum.com>
	<20120105175106.6FAD9B852@mail.bitblocks.com>
	<ea7157b338d53727cc50bd6fee724a5f@chula.quanstro.net>
Date: Thu,  5 Jan 2012 10:25:46 -0800
From: Bakul Shah <bakul@bitblocks.com>
Message-Id: <20120105182546.D1AF3B858@mail.bitblocks.com>
Subject: Re: [9fans] venti and "contrib": RFC
Topicbox-Message-UUID: 558c9fa8-ead7-11e9-9d60-3106f5b1d025

On Thu, 05 Jan 2012 13:01:52 EST erik quanstrom <quanstro@quanstro.net>  wrote:
> > if you read 1TB, you have 8% chance of a silent bad read
> > sector.  More important to worry about that in today's world
> > than optimizing disk space use.
>
> do you have a citation for this?  i know if you work out the
> numbers from the BER, this is about what you get, but in
> practice i do not see this 8%.  we do pattern writes all the
> time, and i can't recall the last time i saw a "silent" read error.

Silent == unseen! Do you log RAID errors? Only way to catch them.

That number is derived purely on an bit error rate (I think
vendors base that on the Reed-Solomon code used). No idea how
"uniformly random" the data (or medium) is in practice. I
thought the "practice" was worse!