Being a generator is a requirement for that.
Alex <creamyfish@xxxxxxxxx> wrote:
>I think when David says 'generator', he doesn't mean the generator of
>the order
>8 Galois field, he means an arbitrary set of number in it which can
>render the
>system of equations solvable to up to a certain number of data
>disks(not necessarily
>255). He uses a brute-force method with the help of a Python program to
>actually
>figure that out. It looks pretty cool to me since I have known the
>system of 4 equations
>generally fails to render a solution for a while, but now I know
>exactly how many ways
>it may fail...
>
>Cheers,
>Alex
>
>
>On Fri, Apr 20, 2012 at 2:16 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
>> On 04/17/2012 01:18 PM, David Brown wrote:
>>>
>>> For quad parity, we can try g3 = 8 as the obvious next choice in the
>>> pattern. Unfortunately, we start hitting conflicts. To recover
>missing
>>> data, we have to solve multiple simultaneous equations over G(2⁸),
>whose
>>> coefficients depend on the index numbers of the missing disks. With
>>> parity generators (1, 2, 4, 8), some of these combinations of
>missing
>>> disk indexes lead to insoluble equations when you have more that 21
>disks.
>>>
>>
>> That is because 255 = 3*5*17... this means {02}^3 = {08} is not a
>generator.
>>
>> -hpa
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid"
>in
>> the body of a message to majordomo@xxxxxxxxxxxxxxx
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Sent from my mobile phone. Please excuse brevity and lack of formatting.
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
