Shown below is a RAID-DP (i.e., RAID6 with dual parity) disk system. D1, D2, D3 and D4 are the data disks. RP is the horizontal or row parity disk and DP is the diagonal parity disk. For the purposes of this problem, each strip or block on a disk is a 4-bit pattern. The horizontal parity block for each row is the exclusive-OR of the four 4-bit data disk blocks within the row. The coloring scheme indicates which data blocks comprise each diagonal. Data blocks that are the same color are exclusive-Ored together to obtain the corresponding diagonal parity block on the DP disk. Blocks can be identified by the combination of the disk name (D1, D2, D3, D4, RP or DP) on which the block resides and the block color ( blue, purple, white, red or orange). The purple block on D1 (D1_purple) is to be overwritten with the new 4-bit pattern shown in the diagram.

a) What is the minimum number of blocks that must be read as a result of writing D1_purple (name each block that must be read)?

b) What is the minimum number of blocks that must be written and what is the name and new 4-bit contents of each block that must be written?

D1 D2 D3 D4 RP DP replaces 1001 1011 1110 1110 0011 0110 0011 0011 0010 0101 1110 0100 0101 0101 1100 0010 0100 0101 1010 1100 0011 1000 1101 1011