If the remaining lives 554 do not satisfy the first addition condition, the storage controller 10 determines whether the life consumption rates 557 of the SSDs 20 included in each parity group PG satisfy a second addition condition or not (step S402). For instance, the storage controller 10 determines whether a statistic of the life consumption rates 557 of the SSDs 20 included in the parity group PG is equal to or greater than a rate threshold or not. In this case, the storage controller 10 determines that the life consumption rates 557 satisfy the second addition condition if the statistic of the life consumption rates 557 is smaller than the rate threshold, or determines that the life consumption rates 557 do not satisfy the second addition condition if the statistic of the life consumption rates 557 is equal to or greater than the rate threshold. The rate threshold is three, for instance.

If the life consumption rates 557 do not satisfy the second addition condition, the storage controller 10 ends the processing. If the remaining lives 554 satisfy the first addition condition or if the life consumption rates 557 satisfy the second addition condition, by contrast, the storage controller 10 transmits notification information requesting addition to the SSDs 20, to the management host device 3 (step S403) and ends the processing.

FIG. 16 is a flow chart for description of an example of the first data distribution processing of step S10 in FIG. 11.