RAID 6 generator

Define the generators to rebuild data from a RAID 6 with 2 missing drives.

Generator formula

Sequential (1, 2, 3, 4, ...)

The generators are sequential numbers starting from one.

Exponential (1, 2, 4, 8, ...)

The generators are powers of two, starting from the zeroth power of two, or 1.

Generator rotation

Rotate with parity blocks

In computing generator values, the starting column (generator=1) is the column following the second parity (Q) column. If the second parity column is the last column, then the starting column is the first column.

Static

The generator starting column is always the first column regardless of the position of the parity columns. (Note that if the box Skip parity blocks below is checked then the starting column is the first non-parity column.)

Skip parity blocks

Whether to skip parity columns in computing generator values. For example in a 4-drive RAID 6 configuration a row may have the following:

• First column: Data block A
• Second column: P Parity
• Third column: Q parity
• Fourth column: Data block B.

Data block A is in the starting column and has generator value 1. If this box is checked block B will have generator value 2. If it is not checked the value will be 4 (if sequential) or 8 (if exponential).