A command portal enables a host system to send non-standard or “vendor-specific” storage subsystem commands to a storage subsystem using an operating system (OS) device driver that does not support or recognize such non-standard commands. The architecture thereby reduces or eliminates the need to develop custom device drivers that support the storage subsystem's non-standard commands. To execute non-standard commands using the command portal, the host system embeds the non-standard commands in blocks of write data, and writes these data blocks to the storage subsystem using standard write commands supported by standard OS device drivers. The storage subsystem extracts and executes the non-standard commands. The non-standard commands may alternatively be implied by the particular target addresses used. The host system may retrieve execution results of the non-standard commands using standard read commands. The host-side functionality of the command portal may be embodied in an API that is made available to application developers.