text: A minimum of one USB flash drive with the correct master access key is required to unlock 
  access to encrypted data after a system restart such as a system-wide reboot or power loss. 
  No USB flash drive is required during a warm reboot, such as a node exiting service mode or 
  a single node reboot. The data center power-on procedure needs to ensure that USB flash 
  drives containing encryption keys are plugged into the storage system before it is powered 
  on. 
  
  During power-on, insert USB flash drives into the USB ports on two supported canisters to 
  safeguard against failure of a node, node’s USB port, or USB flash drive during the power-on 
  procedure. 
  
  To enable encryption by using USB flash drives as the only encryption key provider, complete 
  the following steps: 
  
  1. 
  In the Enable Encryption wizard Welcome tab, select**USB flash drives**and click**Next**, as 
  shown in Figure 12-24. 