0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">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" <mrbrklyn-at-panix.com">mrbrklyn-at-panix.com> wrote:



Not even looked at it outside of the library.=C2=A0 I'm burning up tryi=
ng to

catch up.=C2=A0 Do you have some preliminary work?



I did give it throught.=C2=A0 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 sli=
de

>> come from.=C2=A0 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 mathr>
>>

>> Note that X is XOR for whatever UFT reason

>>

>>

>> REDUNDANCY In the event of a drive failure, the parity drive is ac=
cessed

>> and data is reconstructed from the remaining devices. Once the fai=
led

>> drive is replaced, the missing data can be restored on the new dri=
ve 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 fo=
r the

>> ith bit is calculated as follows:

>>

>> X4(i) =3D 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) =3D X4(i) { X3(i) { X2(i) { X0(i)

>>

>>

>> file:///home/ruben/william stallings - computer organization andr>
>> architecture designing for performance (8th edition).pdf

>>

>> Page 202

>>

>>

>>

>> et=3D"_blank">http://www.nylxs.com/images/raid3_parity_math.png

>>

>> Ruben

>>