HP 3PAR InForm OS 3.1.1 Concepts Guide

only create read-only copies of a base volume. See Figure 7 (page 47) for an example of alternating
read-only and read/write virtual copy relationships.
Figure 7 Alternating Read-only and Read/Write Virtual Copies
See Figure 8 (page 47) for a more complex example of the possible relationships between a parent
base volume and its virtual copies.
Figure 8 Base Volume and Virtual Copy Relationships
Copy-on-Write Function
When a virtual volume or snapshot’s source volume is written to, the copy-on-write function preserves
the data that is to be overwritten. The data is copied to the snapshot space associated with the
original virtual volume before the write operation is completed, and a pointer in the administration
space points to the copied data.
See Figure 9 (page 48) for an example of a sequence of snapshots.
Virtual Copy Snapshots 47