Intel
®
81341 and 81342—Application DMA Unit
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
496
Order Number: 315037-002US
The P+Q RAID-6 Generation matrix contains the coefficients used in calculating the P
and Q check values, based on the Galois Field Matrix multiplication provided in
. Where P is the simple XOR of the source data (The result of the GF Multiply
is equal to the source data with coefficient equal to 1). The Q generation coefficients
(G(0), G(1), G(2),…G(N-1)), are computed from the Vandermond matrix based on the
array data disk count N.
The P and Q check values are computed by the ADMA using a single descriptor. The
P+Q descriptor generates the “P” check value, where the GF Multiplier byte values are
equal to 1 (first row of generation matrix). Concurrently, the ADMA generates the “Q”
check value, where the GF Multiplier byte values are G(0), G(1), G(2),...G(N-1)
(second row of generation matrix).
Figure 62. P+Q RAID-6 Generation Equation
=
X
Generation Matrix (nx2)
1
G(0)
1
G(1)
1
G(2)
1
G(N-1)
1
G(0)
Data
D(0)
D(1)
D(2)
. . .
D(N-1)
Q
Check
P
B6229-01