text: With IBM Spectrum Virtualize, free space does not need to be maintained and managed in 
  each storage subsystem, which further increases capacity usage. Today, it is typical that open 
  systems run at less than 50% of the usable capacity that is provided by the RAID disk 
  subsystems. 
  
  The use of the installed raw capacity in the disk subsystems shows usage numbers of less 
  than 35%, depending on the RAID level that is used. A block-level virtualization solution, such 
  as IBM Spectrum Virtualize, can allow a significant increase to approximately 75 - 80%. 