On Tue, Aug 10 at 21:57, Peter Taps wrote:
Hi Eric,
Thank you for your help. At least one part is clear now.
I still am confused about how the system is still functional after one disk
fails.
The data for any given sector striped across all drives can be thought
of as:
A+B+C = P
where A..C represent the contents of sector N on devices a..c, and P
is the parity located on device p.
From that, you can do some simple algebra to convert it to:
A+B+C-P = 0
If any of A,B,C or P are unreadable (assume B), from simple algebra,
you can solve for any single unknown (x) to recreate it:
A+x+C = P
A+x+C-A-C = P-A-C
x = P-A-C
and voila, you now have your original B contents, since B=x.
--eric
--
Eric D. Mudama
edmud...@mail.bounceswoosh.org
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