first pre-emptive raid

[prad]

On Sat, 28 Jun 2008 13:02:20 +0200
Pieter de Goeje <pieter at degoeje.nl> wrote:

> Parity is calculated using the following formula: 
>
pieter, that is absolutely beautiful!!
it was really bothering me how you can recover data that really wasn't
'there'.

my son and i just worked out the mechanism with some nibbles:

0110 d0
0011 d1
0010 d2
====
0111 p

so

0111 p     0111 p     0111 p
0011 d1    0110 d0    0110 d0
0010 d2    0010 d2    0011 d1
====       ====       ====        
0110 d0    0011 d1    0010 d2

and just extend the concept from nibbles to blocks.

why in diagram 20-3 of the handbook do they show 2 parity blocks though
for disk3 and disk4? why would you ever have more than 1 for any single
disk?


-- 
In friendship,
prad

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