Flushing dirty pages from page buffers indicated by non-sequential page descriptors

A data storage system comprising:

• at least one storage processor including processing circuitry and a memory;
• a plurality of non-volatile data storage drives communicably coupled to the storage processor;
• and
• wherein the memory has program code stored thereon, wherein the program code, when executed by the processing circuitry, causes the processing circuitry to:
• persistently store dirty pages of cached user data received by a data storage system to page buffers that are allocated from a page buffer pool and indicated by page descriptors that are allocated at a head of a temporally ordered page descriptor ring as the dirty pages are stored to the page buffers;
• and
• perform a flush operation by selecting a work-set of non-sequential page descriptors within the page descriptor ring, flushing dirty pages from page buffers indicated by the page descriptors in the work-set to non-volatile data storage drives of the data storage system, and storing, for each one of the page buffers indicated by the page descriptors in the work-set, an indication that the page buffer is available for re-use.