Regrouping data during relocation to facilitate write amplification reduction

A data storage system, comprising:

• flash controller memory;
• and
• a flash controller coupled to the flash controller memory, wherein the flash controller is configured to:
• receive, from a host, a plurality of host write requests including at least first, second, and third host write requests, wherein each host write request of the plurality of host write requests includes write data, a target address to which the write data is to be written, and a stream indicator separate from the write data and the target address, said stream indicator indicating which of multiple different streams of the host is associated with said each host write request, and wherein the stream indicator of at least the first host write request indicates a different one of the multiple different streams than the stream indicator of the third host write request;
• based on receiving the plurality of host write requests:
• store write data of the first host write request in pages of a first logical erase block (LEB) within the storage system and store write data of the second host write request in pages of a different second LEB within the storage system;
• and
• record respective first regrouping metadata for the pages of the first LEB and second regrouping metadata for pages of the second LEB, wherein the first regrouping metadata for the pages written based on the first host write request and second regrouping metadata for pages written based on the second host write request both indicate a same particular stream among the multiple different streams of the host;
• select, based on the first and second regrouping metadata both indicating the particular stream, the first LEB and the second LEB for regrouping;
• and
• regroup valid pages associated with the particular stream from the selected first and second LEBs together and writing the valid pages in a same write operation into a same third LEB.

A program product, the program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a controller of a data storage system, to cause the controller to:

• receive, from a host, a plurality of host write requests including at least first, second, and third host write requests, wherein each host write request of the plurality of host write requests includes write data, a target address to which the write data is to be written, and a stream indicator separate from the write data and the target address, said stream indicator indicating which of multiple different streams of the host is associated with said each host write request, and wherein the stream indicator of at least the first host write request indicates a different one of the multiple different streams than the stream indicator of the third host write request;
• based on receiving the plurality of host write requests:
• store write data of the first host write request in pages of a first logical erase block (LEB) within the storage system and store write data of the second host write request in pages of a different second LEB within the storage system;
• and
• record respective first regrouping metadata for the pages of the first LEB and second regrouping metadata for pages of the second LEB, wherein the first regrouping metadata for the pages written based on the first host write request and second regrouping metadata for pages written based on the second host write request both indicate a same particular stream among the multiple different streams of the host;
• select, based on the first and second regrouping metadata both indicating the particular stream, the first LEB and the second LEB for regrouping;
• and
• regroup valid pages associated with the particular stream from the selected first and second LEBs together and writing the valid pages in a same write operation into a same third LEB.