Buffer write in a solid state drive

A storage device is .provided for direct memory access, such as a PCI express card having a flash memory controller or a RAID controller. A controller performs a mapping of a window of memory addresses to a logical block addressing (LBA) range of the storage device. A host request specifying a write address within the window of memory addresses, leads the controller to initialize a memory buffer and associates it with a first address range. The controller writes to the first memory buffer based on the write address. Responsive to the buffer being full, the controller persists contents of the first memory buffer to the storage device using logical block addressing based on the mapping. Similar read for memory buffer addressing within a window may be provided, with further buffers being initiated for further address ranges, and a free list of buffers kept. Data may be merged to form new stripes when persisting data.