Patent attributes
A subset of drives with protection groups that have D data members and P parity members is scaled in single drive increments. A plurality of indexed partitions equal in size and number are created on (D+P) indexed drives. Protection groups that have D data members and P parity members are created on individual partition indexes of the (D+P) drives. When a new drive is added some of the protection group members located on the (D+P) drives are selected using modulo arithmetic. The selected protection group members are relocated to the new drive and new protection groups are created using the partitions made available due to the relocations. When (D+P) new drives have been added the drive subset may be split into two drive subsets. The modulo arithmetic may include selecting the members of protection group X that are on partition X of drive Y that satisfy the condition (X−Y+N−1) modulo W=0, where N is a count of new drives added to the (D+P) drives and W=(D+P). Alternatively, the modulo arithmetic may include selecting the members of protection group X on partition X of drive Y that satisfy the condition (X+Y−N−1) modulo W=0.
