Could you translate this into English? P' = P + D_n + D_n' Q' = Q + g^n * D_n + g^n * D_n'
I understand this much: P =old parity D_n =old data block(s) P' =new parity D_n' =new data block(s)
But is "+" = xor?
I am lost on this one: Q' = Q + g^n * D_n + g^n * D_n'
With the parity (xor) it can be done by the bit, so an example is easy. Can Q be done by the bit, and if so, could you give an example?
If it takes more than 10 minutes, just tell me it is magic! :)
See my paper on the subject:
http://www.kernel.org/pub/linux/kernel/people/hpa/raid6.pdf
Also, on a related subject.... I have a 14 disk RAID5 with 1 spare. Once RAID6 seems safe and stable I had hoped to convert to a 15 disk RAID6. Is 15 disks too much for RAID6? Any idea what a reasonable limit would be?
The limit is 27 disks total, it's imposed by the md system rather than RAID-6; RAID-6's inherent limit is 254+2 (see, again, the paper.)
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