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Chapter 2 Data Replication
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If the activity between volumes with the pair setting is the Replicate or Restore state, you can change the
copy method of data between MV and RV according to the load status of the disk array. The state to
which a transition is made by the instruction to change the copy method is called the “copy control state“.
There are the following two types of copy between MV and RV in the Replicate or Restore state.
• Copy for reflecting difference
Copy to reflect the content of MV (RV for Restore) at Replicate or Restore to RV (MV for Restore).
• Copy to reflect updates in MV to RV
Copy to reflect updates in MV to RV after Replicate or Restore. However, if Restore(protect) is
executed, the updated data of the MV is not reflected into the RV.
You can change the copy method and state by changing the copy control state.
There are the following copy states in the copy control states as shown in Table 2-2.
Table 2-2 Copy Control State
Copy Control State Copy State
Synchronous Copy
Mode
• Copy for reflecting difference is performed.
• Updates to MV are reflected RV sequentially.
Foreground Copy
Semi-synchronous Copy
Mode
• Copy for reflecting difference is performed.
• I/O of updates to MV is completed when data is written to MV,
and the data is copied to RV immediately after that.
• Can be set for a RemoteDataReplication pair.
Background Copy -
• Copy for reflecting difference is performed.
• I/O of updates to MV is completed when data is written to MV,
and the data is accumulated as difference information. For the
accumulated difference, data is copied to RV asynchronously.
The copy interval to RV (Background Copy Level) can be
changed in units of disk arrays.
Suspend
• Copy for reflecting difference is not performed.
• I/O of updates to MV is completed when data is written to MV,
and the data is accumulated as difference information.
Reflection to RV is not performed.
Suspend
Suspend due to a failure
• Forcefully suspended in the disk array due to a copy fault.
• Copy for reflecting difference is not performed.
• I/O of updates to MV is completed when data is written to MV,
and the data is accumulated as difference information.
Reflection to RV is not performed.