text: **2.5.8 Dense expansion drawers**
  
  Dense expansion drawers, or dense drawers, are optional disk expansion enclosures that are 
  5U rack-mounted. Each chassis features two expansion canisters, two power supplies, two 
  expander modules, and a total of four fan modules. 
  
  Each Dense Drawer can hold up 92 drives that are positioned in four rows of 14 and another 
  three rows of 12 mounted drives assemblies. Two Secondary Expander Modules (SEM) are 
  centrally located in the chassis. One SEM addresses 54 drive ports, and the other addresses 
  38 drive ports. 
  
  The drive slots are numbered 1 - 14, starting from the left rear slot and working from left to 
  right, back to front. 
  
  Each canister in the Dense Drawer chassis features two SAS ports numbered 1 and 2. The 
  use of SAS port1 is mandatory because the expansion enclosure must be attached to an IBM 
  Storwize V7000 node or another expansion enclosure. SAS connector 2 is optional because it 
  is used to attach to more expansion enclosures. 
  
  Each IBM Storwize V7000 can support up to four dense drawers per SAS chain. 