IBM V7000 Introduction And Implementation Manual page 361

You need to confirm the number of MDisks you need to remove (Figure 8-32). If you have
data on the MDisks, and you still need to remove the MDisks from the pool, select the
Remove the MDisk from the storage pool even if it has data on it. The system migrates
the data to other MDisks in the pool check box.
Figure 8-32 Confirm the removal of MDisk from the pool
Available capacity: Make sure that you have enough available capacity left in the storage
pool for the data on the MDisks to be removed.
Chapter 8. Storage pools
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