When constructing a data flow containing Hitachi Block based storage devices, it is necessary to use the correct combination of mover type (Batch or Live/Continuous) in conjunction with a given snapshot or replication technology (Thin Image, Refreshed Thin Image, ShadowImage, TrueCopy, Universal Replicator or Global-Active Device).
The term Differential Snapshot means that a new target volume(s) is created each time the operation is triggered. The target volume(s) remain suspended after creation. The target records the deltas so the source is also required to reconstruct the full data set.
The term Refreshed Snapshot means that a new static target volume(s) is created the first time the operation is triggered. The same target volume(s) is refreshed with new deltas from the source on subsequent triggers. The target volume(s) remain suspended after creation. The target records the deltas and thus the source is also required to reconstruct the full data set.
The term Batch Replication means a static target volume(s) is created the first time the operation is triggered. After initial synchronization, the replication is suspended. Subsequent triggers result in a resynchronization from the source, after which the target volume(s) are suspended.
The term Live Replication means a static target volume(s) is created the first time the operation is triggered. The source and target volume(s) are continuously kept in sync (paired) either by copy-on-write (COW) or copy-after-write CAW) data transfer mechanisms. The replication pairs can be paused and resumed as required.
| Scenario | Mover | Description |
|---|---|---|
| Thin Image Snapshot (TI) | Batch | About Thin Image and Thin Image Advanced differential and refreshed snapshots |
| ShadowImage Replication (SI) | Batch or Live | About ShadowImage replication |
| TrueCopy Replication (TC) | Live | About TrueCopy replication |
| Universal Replicator (UR) | Live | About Universal Replicator |
| Global-Active Device (GAD) | Live | About Global-Active Device replication |
| Three Data Centre Cascade (TC+UR) |
Live TC + Live UR |
About three datacentre cascade (3DC) |
| Three Data Centre Multi Target (TC+UR) |
Live TC + Live UR |
About three datacentre multi-target |
| Clones of a Clone (SI+SI) |
Batch SI(1) + Batch SI |
About static clones of a clone |
| Clone with Replication (SI+GAD) |
Batch SI(1) + Live GAD |
About clone with replication |
| Snapshot with Replication (TI+GAD) |
Batch TI + Live GAD |
About snapshot with replication |
| Snapshot of a Clone (SI+TI) |
Batch SI(1) + Batch TI |
About snapshot of a clone |
| Replication of a Clone (SI+TC or SI+UR) |
Batch SI(2) + Batch TC or UR |
About replication of a clone |
| Remote Snapshot (TC+TI or UR+TI) |
Live TC or UR + Batch TI |
About remote snapshot |
| Local and Remote Snapshots (TC+TI/TI, UR+TI/TI or GAD+TI/TI) |
Live TC, UR or GAD + Batch TI |
About local and remote snapshots |
| Remote Clone (TC+SI or UR+SI or GAD+SI) |
Live TC, UR or GAD Batch SI(1) |
About remote clone |
| Local and Remote Clones (TC+SI/SI or UR+SI/SI or GAD+SI/SI) |
Live TC, UR or GAD Batch SI(1) |
About local & remote clones |
| Local Snapshot and Remote Clones (TC+TI/SI or UR+TI/SI or GAD+TI/SI) |
Live TC, UR or GAD + Batch TI + Batch SI(1) |
About local snapshot and remote clones |
| Remote Snapshot and Local Clones (TC+SI/TI or UR+SI/TI or GAD+SI/TI) |
Live TC, UR or GAD + Batch SI(1) + Batch TI |
About local snapshot and remote clones (reversed) |
(1) Continuous SI can also be used in these topologies to vary the use case.
(2) Continuous SI cannot be used in these topologies since it is not possible to chain a remote replication from Continuous SI.