text: Figure 13-5 SAS cabling with numbering of enclosures 
  
  At system initialization, when devices are added to or removed from strands, IBM Storwize 
  V7000 performs a discovery process to update the state of the drive and enclosure objects. 
  
  **13.1.5 Power**
  
  All enclosures accommodate two power supply units (PSUs) for normal operation. A single 
  PSU can supply the entire enclosure for redundancy. For this reason, it is highly advised to 
  supply AC power to each PSU from different Power Distribution Units (PDUs). 
  
  There is a power switch on the power supply and indicator LEDs. The switch must be on for 
  the PSU to be operational. If the power switch is turned off, the PSU stops providing power to 
  the system. 
  
  For control enclosure PSUs, the battery integrated in the node canister continues to supply 
  power to the node. A fully charged battery is able to perform two fire hose dumps. It supports 
  the power outage for 5 seconds before initiating safety procedures. 