The code in Microsoft Windows that converts a hexadecimal device ID to an ASCII string may drop the most significant nibble in each byte if the byte is less than 0×10. (The most significant nibble is 0.) This causes different disks to be identified as the same disk by Multipath I/O (MPIO). At the very least, this may cause problems in mounting affected disks. And architecturally, this could cause data corruption.
When you apply this hotfix, the conversion algorithm is fixed. Disks that were masked by this issue before you installed the hotfix may be raw disks that still have to be partitioned and formatted for use. After you apply this hotfix, check in Disk Management or Diskpart for previously hidden disks.
A supported hotfix is available from Microsoft Support.