[clug-talk] RAID Question
me at jonwatson.ca
Tue Oct 10 20:34:29 PDT 2006
I'm going to bed soon, promise. Just one more question about RAID5: In a
3 disk RAID5, the parity bit can be used to derive the missing
information if one of the disks fails. I think.
The rather simplistic example in my book has is the following (each
column represents one disk)
22 12 34
65 68 3
13 9 4
the parity bits are 34, 68, and 13.
So, my question is - say, for example, that disk 3 goes down. I am
therefore left with
How does the system know when to add and when to subtract to get the
missing values? Like how does it know not to do 22-12 and end up with 10
instead of 34?
Or 65 + 68 = 133 instead of 68-65 = 3?
Pointers, thoughts, and links welcome.
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