HP XP P9500 Storage - Manual (Page 10)

Initial and update copy operations
When you create a pair, the storage system executes an initial copy. When the pair is created,
the storage system asynchronously copies updates received by the primary volume to the secondary
volume.
Initial copy
When you create a pair, the initial copy is started by the storage system, and all the data in the
primary volume is copied to the secondary volume.
•
Before the pair is created, the pair’s status is SMPL.
•
While the initial copy is in progress, the status is COPY(PD)/COPY.
•
The status changes to PAIR when the initial copy is complete.
Figure 3 Initial copy operation
A primary volume continues receiving updates from the host during the initial copy. When the
initial copy is completed, update copy operations start.
Update copy
I/O sent to the primary volume in PAIR status is marked as differential data and stored in bitmaps
for transfer to the secondary volume. Update copy operations are performed periodically by the
storage system. The timing of the update copy operation is based on the amount of differential
data that accumulates and the elapsed time since the previous update.
10 Business Copy overview