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## 3.6.4 Remote copy 

Click Remote Copy  to open the window that is shown in Figure 3-78. This window shows the existing remote copy relationships, and you can set up and modify consistency groups. From this window, you can also start and stop relationships, add relationships to a consistency group, and switch the direction of the mirror. 

<img src='content_image/984126.jpg'>

The menu provides the options to create Metro Mirror, Global Mirror, or Global Mirror with Changed Volumes: 

Metro Mirror 

Global Mirror 

Global Mirror with Changed Volumes 

This option makes synchronous  copies. The original write operations are not considered complete until the write operation to the destination disk is confirmed. The distance between your two sites is determined by how much latency your applications can handle. 

This option makes asynchronous  copies of your disk. The write is considered complete after it is complete at the local disk. It does not wait for the write to be confirmed at the remote cluster as Metro Mirror does. This method greatly reduces the latency that is experienced by your applications if the other cluster is far away. 

However, it also means that during a failure, the data on the remote copy might not contain the most recent changes that were committed to the local disk. 

This option is best described as “Continuous Remote FlashCopy.” If you use this feature, IBM Spectrum Virtualize essentially takes a periodic FlashCopy of a disk and writes it to your remote destination. This feature completely isolates the local copy from wide area network (WAN) issues and from sudden spikes in workload that might occur. 

The drawback is that your remote copy might lag behind the original by a significant amount of data, depending on how you set up the cycle time. 

