Error tolerance is increased for a storage system having a plurality of
arrays by making local redundancy in a selected array globally available
throughout the storage system. To achieve the increased error tolerance,
a donor array is selected from the plurality of arrays when the
difference between a minimum Hamming distance of the donor array and a
minimum Hamming distance of a recipient array is greater or equal to 2. A
donor storage unit is selected in the donor array and recipient
information is then rebuilt from the recipient array on the selected
storage unit. The selected storage unit is indicated to the donor array
as having been donated before the lost information is rebuilt on the
selected storage unit. Preferably, the minimum Hamming distance of the
recipient array is d.gtoreq.2 before the donor array is selected from the
plurality of arrays.