512 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
Figure 11-81   Restoring a snapshot summary
If you chose to restore the data from the cloud to a new volume, the new volume appears 
immediately in the volumes window. However, it is taken offline until all the data from the 
snapshot is written. The new volume is totally independent. It is not defined as a target in a 
FlashCopy mapping with the selected volume for example. It also is not mapped to a host.
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.
Regardless of which option you choose, Volume mirroring can provide extra protection for 
your environment.