## Storage Device Driver Reference

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### Non-Removable (Partitionable) Media

16h Get Partitionable Disk Count
17h Map Unit Numbers to Physical Drive

16h - Get Partitionable Disk Count: The number of non-removable drives is returned.

17h - Map Unit Numbers to Physical Drive: The request packet unit field indicates a non-removable drive number that is zero-based. OS2DASD adds Function 80h and searches for VolCBs associated with that particular physical unit. A bit map of unit numbers associated with the physical drive is returned. The bit numbering scheme for the bit mask corresponds to 2**(unit number) in a ULONG field.