F7 software RAID docs?

[Benjamin Franz]

On Thu, 9 Aug 2007, Neal Becker wrote:

> Bruno Wolff III wrote:
>
>> What are you going to be doing that makes you think raid 0 is desirable?
>> For modern home machines with lots of memory, this probably isn't going to
>> give you much of a speed up in typical use. It will make the chances of
>> your file system being lost because of a hardware problem, about double.
>> Raid 1 or 10 seem to be more useful for home users, than raid 0.
>>
>
> No!  If the prob of failure during an interval T is pf, the prob of failure
> for an array of 2 drives during T is 1 - (1-pf)^2.

Which, for probabilities typical of hard drives, is *very* close to twice 
the probability of a single drive failure. Do the actual math. Even at 10% 
failure rates (!!!!) the difference between 2X (20%) and 1 - (1-pf)^2 
(19%) is insignificant for all practical purposes. You won't reach 
probabilities high enough to care about the difference before the drives 
are obsolete and replaced anyway.

-- 
Benjamin Franz

"It is moronic to predict without first establishing an error rate
  for a prediction and keeping track of one’s past record of accuracy."
                     -- Nassim Nicholas Taleb, Fooled By Randomness