Embodiments relate to a system, program product, and method for expanding the retention capacity of a write cache on a host bus adaptor (HBA) device through the use of non-volatile dual in-line memory modules (NVDIMMs). At least a portion of the existing NVDIMM capacity is leveraged to temporarily retain data that is to be written to persistent storage to reduce the potential for data loss during external electric power disruptions. A NVDIMM HBA Write Cache Module (NHWCM) facilitates the data file traffic transmission and I/O command generation and transmission between a processing device, the HBA device, the NVDIMMs, and the persistent storage.