444 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
Read from the source Volume
When a user performs a read operation on the source volume, there is no redirection. The 
operation is similar to what is done with a volume that is not part of a FlashCopy mapping.
Write on the source Volume
Performing a write operation on the source volume modifies a block or a set of blocks, which 
modifies a grain on the source. It generates one of the following actions, depending on the 
state of the grain to be modified:
/SM590000If the bitmap indicates that the grain was copied, the source grain is changed and the 
target volume and the bitmap table remain unchanged, as shown in Figure 11-5.
Figure 11-5   Modifying an already copied grain on the Source
/SM590000If the bitmap indicates that the grain was not yet copied, the grain is first copied on the 
target (copy on write), the bitmap table is updated, and the grain is modified on the source, 
as shown in Figure 11-6.
Figure 11-6   Modifying a non-copied grain on the source
Write on a Target Volume
Because FlashCopy target volumes are immediately accessible in Read and Write mode, it is 
possible to perform write operations on the target volume when the FlashCopy mapping is 
started.