## Storage Device Driver Reference

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### Introduction to ASPI

ASPI is an application interface that allows easier access to SCSI devices. When running DOS, users typically load an ASPI manager that routes all requests directly to the hardware. ASPI drivers (such as ASPIDISK and ASPICD) send requests to the ASPI manager, which then sends the command to the appropriate device.

The device driver model used by OS/2 is layered (similar to ASPI) so that an adapter device driver (ADD) is responsible for knowing about the hardware dependencies of a particular SCSI adapter. Applications that want to send ASPI requests do so by routing these requests to a device manager ( OS2ASPI.DMD) and then converts them into requests recognizable to any ADD.

The ASPI support currently embedded within OS/2 2.x allows any OS/2 application to send commands to a SCSI device. However, there are a large number of DOS and Windows applications that could be supported if the commands were routed to OS2ASPI.DMD.

VASPI.SYS is a virtual device driver that allows DOS applications to issue SCSI commands that will be handled by OS2ASPI.DMD. If you have an existing DOS or Windows ASPI application, it should now be able to run in a virtual DOS session under OS/2 2.x.