A failed DiskDriveExtent can be spared.
The DiskDriveExtents associated can be used to spare or replace other DiskDriveExtents that might fail, as shown in Figure 1.
Figure 1. Association during failure
In this relationship between the new DiskDriveExtent and the array being rebuilt, a failed DiskDriveExtent is being spared by the new one. The IBMTSSVC_Spared associations remain until the sparing process is complete.