text: **11.6.18 Practical use of Global Mirror**
  
  The practical use of Global Mirror is similar to the Metro Mirror as described in 11.6.9, 
  “Practical use of Metro Mirror” on page 523. The main difference between the two remote 
  copy modes is that Global Mirror and Global Mirror with Change Volumes are mostly used on 
  much larger distances than Metro Mirror. Weak link quality or insufficient bandwidth between 
  the primary and secondary sites can also be a reason to prefer asynchronous Global Mirror 
  over synchronous Metro Mirror. Otherwise, the use cases for MM/GM are the same. 
  
  **11.6.19 IBM Spectrum Virtualize HyperSwap topology**
  
  The IBM HyperSwap topology is based on IBM Spectrum Virtualize Remote Copy 
  mechanisms. It is also referred to as an “active-active relationship” in this document. 
  
  You can create an HyperSwap topology system configuration where each I/O group in the 
  system is physically on a different site. These configurations can be used to maintain access 
  to data on the system when power failures or site-wide outages occur. 
  
  In a HyperSwap configuration, each site is defined as an independent failure domain. If one 
  site experiences a failure, then the other site can continue to operate without disruption. You 
  must also configure a third site to host a quorum device or IP quorum application that 
  provides an automatic tie-break in case of a link failure between the two main sites. The main 
  site can be in the same room or across rooms in the data center, buildings on the same 
  campus, or buildings in different cities. Different kinds of sites protect against different types of 
  failures. 