IBM TotalStorage DS300 Best Practices Manual page 196

7. On the Device tab the Flashcopy type Parent can be seen.
Figure 4-159 Flashcopy source logical drive — Device properties
8. The tab Flashcopy children exists only for Flashcopy source logical drives.
This tab lists the dates when the Flashcopy was taken. It also shows the Data
Space and the Virtual space. Data space is the current space required for
this Flashcopy in the array. Virtual space shows the maximum size to which
the Data space can grow up. In worst case this amount of free space is in the
array required. This depends on the amount of changed data in the source or
target logical drive. The figure shows also the second Flashcopy does not
require data space. This is because the COW area and COW lookup table are
shared between those two Flashcopys.
Figure 4-160 Flashcopy children properties of a Flashcopy source logical drive
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IBM TotalStorage DS300 and DS400 Best Practices Guide