The DISK_INFO structure contains information (the drive letter) about the disk device on the server.

 typedef struct _DISK_INFO {
   [string] WCHAR Disk[3];
 } DISK_INFO,
  *PDISK_INFO,
  *LPDISK_INFO;

Disk: The drive identifier of the disk device. This MUST consist of two Unicode UTF-16 characters followed by the null-terminating character (for example, "A:\0"). The first character in this string MUST be a drive letter in the range "A" through "Z", inclusive. The second character MUST be the ":" character.