After the task completes successfully, the GUI shows that encryption is licensed for the  specified node, as shown in Figure 7-23. Although authorization codes and encryption license keys use the same format (four groups  of four hexadecimal digits), you can only use each of them in the appropriate activation  process. If you use an authorization code when the system expects a license key, the system  displays an error message, as shown in Figure 7-24. This section describes the process to create and store system master access key copies,  also referred to as  encryption keys . These keys can be stored on any or both of two key  providers: USB flash drives or a key server. Support for simultaneous use of both USB flash drives and a key server is available in IBM  Spectrum Virtualize code V8.1 and later. Organizations that use encryption key management  servers might consider parallel use of USB flash drives as a backup solution. During normal  operation, such drives can be disconnected and stored in a secure location. However, during  a catastrophic loss of encryption servers, the USB drives can still be used to unlock the  encrypted storage.  The following list of key server and USB flash drive characteristics might help you to choose  the type of encryption key provider that you want to use. 258  IBM FlashSystem 9100 Architecture, Performance, and Implementation 7.4.3 Enabling Encryption Figure 7-24 License key failure Figure 7-23 Successful encryption license activation Problems with manual license activation