Data storage system with write back cache

A method comprising:

• connecting a host to a data storage subsystem, the host comprising a host processor, the data storage subsystem comprising a controller;
• generating write back data at the host;
• allocating a cache location in the data storage subsystem for the write back data with the host processor;
• storing the generated write back data in the allocated cache location;
• writing the generated write back data in a non-volatile destination address as directed by the controller;
• waiting for a first secondary event with the generated data stored in both the cache location and the non-volatile destination address;
• and
• signaling the host processor that the cache location is free for new data in response to detection of the first secondary event.

A method comprising:

• generating write back data for a data storage subsystem;
• allocating a first cache location in the data storage subsystem for the write back data with a hardware processor;
• storing the generated write back data in the first cache location;
• mirroring the write back data to a second cache location of the data storage subsystem;
• writing the write back data in a non-volatile destination address as directed by a data storage subsystem controller;
• waiting for a first secondary event with the write back data stored in the first cache location or the second cache location and the non-volatile destination address;
• and
• signaling the hardware processor that the first or second cache location is free for new data in response to detection of the first secondary event.