HP MSA 1040 SMU Reference Guide (762784-001, March 2014)

About the Remote Snap replication feature 125
• The reserve size is calculated as follows:
• If the primary volume and the snap pool are each less than 500 GB, the reserve will be the same size as the
primary volume.
• If the primary volume is larger than 500 GB, the reserve size will be the maximum, 500 GB.
• If the snap pool is larger than 500 GB, the reserve will be the same size as the snap pool.
• The required space in the vdisk is calculated as follows:
• If the combined size of the primary volume and the reserve is less than the combined size of the primary
volume and the snap pool, the required space is the combined size of the primary volume and the snap pool.
• If the combined size of the primary volume and the reserve is larger than the combined size of the primary
volume and the snap pool, the required space is the combined size of the primary volume and the reserve.
The following table shows examples of how much available space a vdisk must have in order to be shown by the
vdisk option. If you want to replicate a volume whose size is not shown, you can use the above calculations to
determine how much available space the secondary vdisk must have.
Remote replication disaster recovery
Replication can continue in the event of system faults such as:
• Temporary communication failure. Remote replication will retry replication operations according to
user-configured policies.
• Controller failure. In a dual-controller system, failover will occur and the surviving controller will take over
replication processing until controller recovery occurs.
• Disk or power supply failure.
If a disaster causes the primary volume to become inaccessible, you can set the secondary volume to be the primary
volume so that volume can be mapped to hosts. Disaster recovery requires user intervention because decisions must
be made based on the data content of replication volumes and their snapshots.
1. Synchronize the secondary volume to a replication snapshot, preferably a replication sync point. Any data written
to the primary volume since the last-completed replication will not be available.
2. After synchronization, set the secondary volume to be the new primary volume.
Table 11 Available space required for a vdisk to be selectable to contain a secondary volume
Primary volume
size (GB)
Available space
required in
vdisk (GB)
Primary volume
size (GB)
Available space
required in
vdisk (GB)
Primary volume
size (GB)
Available space
required in
vdisk (GB)
100 200 110 0 16 0 0 2100 2600
200 400 12 0 0 170 0 2200 2700
300 600 1300 1800 2300 2800
400 800 1400 1900 2400 2900
500 1000 1500 2000 2500 3000
600 1100 160 0 210 0 2600 3120
700 1200 1700 2200 2700 3240
800 1300 180 0 230 0 2800 3360
900 1400 1900 2400 2900 3480
1000 1500 2000 2500 3000 3600