In addition to sizing journal volumes, you must also consider the following requirements and restrictions:

• Only DP-VOLs whose emulation type is OPEN-V can be used for journal volumes.

  Exceptions are the DP-VOL with Data Direct Mapping attribut enabled or capacity saving enabled, and the deduplication system data volume. They cannot be used as journal volumes.

• Volumes in a virtual storage machine cannot be used as journal volume.
• A journal ID can be used in one virtual storage machine only.
• Volumes to which a path is set from a host cannot be registered as journal volumes.
• Journal volumes must be registered in a journal before the initial copy operation is performed.
• Journal volumes must be registered on both the primary and secondary storage systems.
• You can register two journal volumes in a journal in the primary storage system and in the secondary storage system, but we recommend using one journal volume in each system. The second journal volume becomes the reserve journal volume and is not used for normal operations.
• Journal volumes should be sized according to RPO and write-workload. For details, see Sizing journal volumes .
• Journal volume capacity:
  • Journal volumes in a journal can have different capacities.
  • A master journal volume and the corresponding restore journal volume can have different capacities.
  • The displayed journal volume capacity is the master journal capacity and restore journal capacity. The reserve journal volume is not included in the displayed journal volume capacity.
  • Journal volume capacity is not included in accounting capacity.
  • In the GUI documents the journal volume capacity is called the journal capacity.
  • In the RAID Manager documents the journal volume capacity is called the "capacity for the journal data on the journal volume" and "capacity of the data block size of the journal volume".
• The number of journal volumes in the master journal does not have to be equal to the number of volumes in the restore journal.
• A data volume and its associated journal volume can belong to only one journal.
• Data volumes and journal volumes in the same journal must belong to the same controller.
• Do not register a volume to a journal during quick formatting. Doing so stalls the operation.
• Journal volumes consist of two areas: One area stores journal data, and the other area stores metadata for remote copy.
• If you extend the journal volume when the journal volume size exceeds 36 GB, you need to restore the journal that is used for the extension to the S-VOL to use the extended capacity. However, it might take some time until the extended capacity becomes ready for use.