
616 DS8800 Performance Monitoring and Tuning
Figure 18-15 Remote storage server with D volumes
Figure 18-15 shows the three Global Mirror volumes and the addition of D volumes that you
can create for test purposes. We suggest, as an alternative, a rank with larger and slower
DDMs. The D volumes can be read from another host, and any other I/O to the D volumes
does not affect the Global Mirror volumes in the other ranks. A
nocopy relationship between B
and D volumes reads the data from B when coming through the D volume. So, you might
consider a physical COPY when you create D volumes on a different rank, which separates
additional I/O to the ...