IBM XIV Storage System Copy Services and Migration

4.2.3 Mirroring statusThe status of a mirror is affected by a number of factors such as the links between the XIVs orthe initialization state.Link statusThe link status reflects the connection from the master to the slave volume or CG. A link hasa direction (from local site to remote or vice versa). A failed link or a failed secondary systemboth result in a link error status. The link state is one of the factors determining the mirroroperational status. Link states are as follows:►►OK: link is up and functioningError: link is downFigure 4-5 and Figure 4-6 depict how the link status is reflected in the XIV GUI, respectively.Figure 4-5 Link upFigure 4-6 Link downIf there are several links (at least two) in one direction and one link fails, this usually does notaffect mirroring as long as the bandwidth of the remaining link is high enough to keep up withthe data traffic.Monitoring the link utilizationThe mirroring bandwidth of the links must be high enough to cope with the data traffic causedby the changes on the master volumes. During the planning phase, before setting upmirroring, monitor the write activity to the local volumes. The bandwidth of the links formirroring must be as large as the peak write workload.Chapter 4. Remote Mirroring 79