In RAID 4, data is placed in Strips that are "scattered" over the data disks, so that each subsequent strip is on the next data disk, modulo the number of disks. For this, there is a parity disk that holds the parity bits of zeroth bits, first bits, second bits, etc., equal-numbered strips divided by the number of data disks, for example, strips 0-3, 4-7, 8-11, etc.:

the start of strips 0,1,2,3 looks like this:

In the parity strip, the values are placed so that the parity bit keeps the corresponding strip bits 0-3 odd.

Disk 3 has been damaged and reads only 0. After replacing the disk with a new one, what values should be put in the strip on disk 3?

\begin{tabular}{|l|l|l|l|l|l|} \hline 0 & 1 & 0 & 0 & 1 & Paritydisk \\ \hline 0 & 0 & 0 & 0 & 0 & Disk 3 \\ \hline 1 & 0 & 1 & 1 & 0 & Disk 2 \\ \hline 1 & 0 & 1 & 1 & 0 & Disk 1 \\ \hline 0 & 1 & 1 & 0 & 0 & Disk 0 \\ \hline \end{tabular}