634 Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1
Access to the Metro Mirror target volume is measured and HyperSwap triggers a switch of the
Metro Mirror copy direction, if the workload on the “wrong” site is significantly higher than the
workload on the Metro Mirror source site over any length of time, as shown in Figure 10-160.
This copy direction switch reduces the additional host-related long-distance traffic and
provides better response time.
Figure 10-160 Data flow: Switch copy direction
The duration until the copy direction switches depends on the load distribution on the volume
in both sites. Although a HyperSwap volume can be accessed concurrently for read and write
I/O from any host in any site, all I/O is forwarded to one I/O group in one site. Usage of the
wrong site increases the long-distance traffic. The HyperSwap cluster monitors the workload
and it can switch the copy direction if the highest workload is arriving on the wrong site.
Applications with an equal workload pattern to the same volume by using both I/O groups
(Oracle Real Application Clusters (RAC) and VMware vMotion) are not optimal for local
HyperSwap.
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