MESSAGE
| DATE | 2014-12-06 |
| FROM | Ruben Safir
|
| SUBJECT | Re: [LIU Comp Sci] Parity Bit Algebra
|
From owner-learn-outgoing-at-mrbrklyn.com Sat Dec 6 21:36:08 2014
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Date: Sun, 07 Dec 2014 02:36:44 +0000
From: Ruben Safir
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Subject: Re: [LIU Comp Sci] Parity Bit Algebra
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On 12/06/2014 11:09 PM, Maneesh Kongara wrote:
> Preliminary work as in answers to the other questions of the assignment?
> On Dec 6, 2014 6:08 PM, "Ruben Safir" wrote:
I'm going to crash, how far did you get in the assingment.
Call me is 20 minutes. I have one hour to do it :)
>> On 12/06/2014 10:52 PM, Maneesh Kongara wrote:
>>> Thanks so much for sharing Mr Rubin. Have you completed the assignment?
>>> On Dec 6, 2014 5:49 PM, "Ruben Safir" wrote:
>> Not even looked at it outside of the library. I'm burning up trying to
>> catch up. Do you have some preliminary work?
>>
>> I did give it throught. Part of the solution must have to do with the
>> Comp + 2 binary
>>
>> I can't even find my notes...
>>
>>>> This is from theidiscussion of Raid 3 Stallings Text which the slide
>>>> come from. It is related to the problem you asked about the parity bit
>>>> calculation for the Hamming Code
>>>>
>>>> Not the methodology for logical calculation, it is straight math
>>>>
>>>> Note that X is XOR for whatever UFT reason
>>>>
>>>>
>>>> REDUNDANCY In the event of a drive failure, the parity drive is accessed
>>>> and data is reconstructed from the remaining devices. Once the failed
>>>> drive is replaced, the missing data can be restored on the new drive and
>>>> operation resumed.
>>>>
>>>> Data reconstruction is simple. Consider an array of five drives in which
>>>> X0 through X3 contain data and X4 is the parity disk.The parity for the
>>>> ith bit is calculated as follows:
>>>>
>>>> X4(i) = X3(i) { X2(i) { X1(i) { X0(i)
>>>>
>>>> where { is exclusive-OR function.
>>>>
>>>> Suppose that drive X1 has failed. If we add X4(i) { X1(i) to both sides
>>>> of the preceding equation, we get
>>>>
>>>> X1(i) = X4(i) { X3(i) { X2(i) { X0(i)
>>>>
>>>>
>>>> file:///home/ruben/william stallings - computer organization and
>>>> architecture designing for performance (8th edition).pdf
>>>>
>>>> Page 202
>>>>
>>>>
>>>>
>>>> http://www.nylxs.com/images/raid3_parity_math.png
>>>>
>>>> Ruben
>>>>
>>
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