Read-foreign-slices request for improved read efficiency with bundled writes

A computing device of a dispersed storage network (DSN) comprises:

• memory;
• an interface;
• and
• a processing module operably coupled to the memory and the interface, wherein the processing module is configured to execute the operations of:
• sending, via the interface, a set of read requests to a first set of storage units of the DSN, wherein a read request of the set of read requests is regarding a particular encoded data slice of a set of encoded data slices, wherein the particular encoded data slice has a particular pillar number and a source name, wherein a DSN address for the particular encoded data slice includes the particular pillar number and the source name, wherein a storage unit of the first set of storage units is allocated a DSN address range in which the DSN address of the particular encoded data slice lies, and wherein a decode threshold number of encoded data slices is needed to recover a data segment of a data object;
• sending, via the interface, a set of read foreign requests to a second set of storage units of the DSN, wherein a read foreign request of the set of read foreign requests includes a request to read an encoded data slice having the source name and having a pillar number that creates a DSN address that is outside of the DSN address range of a storage unit in the second set of storage units;
• receiving, via the interface, favorable responses to the set of read requests;
• when a favorable response is received regarding the read foreign request, determining whether the encoded data slice contained in the favorable response regarding the read foreign request is needed to obtain the decode threshold number of encoded data slices;
• when the encoded data slice contained in the favorable response regarding the read foreign request is needed to obtain the decode threshold number of encoded data slices, including the encoded data slice contained in the favorable response regarding the read foreign request with other encoded data slices received in the favorable response to the set of read requests to produce the decode threshold number of encoded data slices;
• and
• decoding the decode threshold number of encoded data slices to recover the data segment.