Efficient method for rebuilding a set of encoded data slices

A computer readable memory comprises:

• a first memory element that stores operational instructions that, when executed by a computing device of a dispersed storage network (DSN), causes the computing device to:
• determine that an encoded data slice requires rebuilding;
• determine that the encoded data slice requiring rebuilding is part of a fan-out encoded data slice group;
• when the encoded data slice is determined to be part of the fan-out encoded data slice group:
• determine whether a copy of a valid encoded data slice of the fan-out encoded data slice group is available;
• when a copy of the valid encoded data slice of the fan-out encoded data slice group is not available, rebuild the encoded data slice to produce a rebuilt encoded data slice;
• a second memory element that stores operational instructions that, when executed by a storage unit of the DSN, causes the storage unit to:
• direct the memory to store the rebuilt encoded data slice;
• and
• create copies of the rebuilt encoded data slice to produce a rebuilt fan-out encoded data slice group.