446 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
Read from a target volume
Performing a read operation on the target volume returns the value in the grain on the source 
or on the target, depending on the bitmap:
/SM590000If the bitmap indicates that the grain was copied from the source or that the grain was 
modified on the target, the grain on the target is read, as shown in Figure 11-9.
/SM590000If the bitmap indicates that the grain was not yet copied from the source or was not 
modified on the target, the grain on the source is read, as shown in Figure 11-9.
Figure 11-9   Reading a grain on target
If the source has multiple targets, the Indirection layer algorithm behaves differently on Target 
I/Os. For more information about multi-target operations, see 11.1.11, “Multiple target 
FlashCopy” on page 452.
Note: The bitmap is not updated in this case. Otherwise, it might be copied from the 
source later if a background copy is ongoing or if write operations are made on the source. 
That process overwrites the changed grain on the target.