text: **11.1.7 Interaction with cache**
  
  IBM Spectrum Virtualize-based systems have their cache divided into upper and lower cache. 
  Upper cache serves mostly as write cache and hides the write latency from the hosts and 
  application. Lower cache is a read/write cache and optimizes I/O to and from disks. 
  Figure 11-10 shows the IBM Spectrum Virtualize cache architecture. 