The FlashCopy Mapping status changes to Stopped, as shown in Figure 10-61. 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, and 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, and 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 timeout 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 -mirror  writepriority redundancy  command to set the redundancy option. Regardless of which option you choose, volume mirroring can provide extra protection for  your environment. Migration offers the following options: Figure 10-61 FlashCopy Mapping status 10.5 Volume mirroring and migration options GLYPH<SM590000> Volume migration by using volume mirroring and then by using Split into New Volume. By  using this option, you can use the available RAID 1 functionality. You create two copies of  data that initially has a set relationship (one volume with two copies, one primary and one  secondary) but then break the relationship (two volumes, both primary and no relationship  between them) to make them independent copies of data.  GLYPH<SM590000> Import to Image mode. By using this option, you can import a storage MDisk or logical unit  number (LUN) with its data from an external storage system without putting metadata on it  so that the data remains intact. After you import it, all copy services functions can be used  to migrate the storage to other locations while the data remains accessible to your hosts.  GLYPH<SM590000> Export to Image mode. By using this option, you can move storage from  managed  mode to  image  mode, which is useful if you are using the IBM Storwize as a migration device. For  example, vendor A’s product cannot communic ate with vendor B’s product, but you must  migrate data from vendor A to vendor B. By using Export to image mode, you can migrate  data by using Copy Services functions and then return control to the native array while  maintaining access to the hosts. Chapter 10. Copy Services  521