text: **11.5 Volume mirroring and migration options**
  
  *Volume mirroring*is a simple RAID 1-type function that enables a volume to remain online 
  even when the storage pool that is backing it becomes inaccessible. Volume mirroring is 
  designed to protect the volume from storage infrastructure failures by seamless mirroring 
  between storage pools. 
  
  Volume mirroring is provided by a specific volume mirroring function in the I/O stack. It cannot 
  be manipulated like a FlashCopy or other types of copy volumes. However, this feature 
  provides migration functionality, which can be obtained by splitting the mirrored copy from the 
  source or by using the*migrate to*function. Volume mirroring cannot control backend storage 
  mirroring or replication. 
  
  With volume mirroring, host I/O completes when both copies are written. This feature is 
  enhanced with a tunable latency tolerance. This tolerance provides an option to give 
  preference to losing the redundancy between the two copies. This tunable time-out value is 
  Latency or Redundancy. 
  
  The Latency tuning option, which is set with**chvdisk -mirrorwritepriority latency**, is the 
  default. It prioritizes host I/O latency, which yields a preference to host I/O over availability. 
  However, you might need to give preference to redundancy in your environment when 
  availability is more important than I/O response time. Use the**chvdisk -mirrorwritepriority**
  **redundancy**command to set the redundancy option. 