This document compares synchronous and asynchronous remote replication technologies from Hitachi, specifically Hitachi TrueCopy and Hitachi Universal Replicator. Hitachi TrueCopy provides synchronous replication where data is written to the target volume at the same time as the primary volume. Hitachi Universal Replicator provides asynchronous replication where data is written to a journal first before being sent and replicated to the target volume, providing less wait time than synchronous replication. A diagram is also included showing the architecture and data flows of these different replication methods between primary, journal, and target volumes located in local and remote data centers.

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Senior Manager Presales
Hitachi Data Systems

2. Realität

4. 1.
2.
3.
4.
Sync - wait
1.
3.
4.
2.
Async – less wait

14. In-region
Data Center
Out of Region
Remote Data Center
JNL
Data Volumes
JNLPrimary Data Volumes
Journal data transfers
Journal read requests
1. Records are written to the primary disk. Meta data and a copy of the data placed in the journal
2. Target system issues journal reads to retrieve data that is ready to be replicated from the journal
(FIFO)
3. Primary system sends the data and metadata from the journal to the target system, including
sequence information
4. Data is committed on the target system – written to S-VOL
5. Once data is committed on the target system, the primary system is notified using the sequence
information and the journal data is released
6. If replication is interrupted and relationship suspended - replication can be restarted and continue
from the point of interruption
WRT
Hitachi
Universal
Replicator™
Asynchronous
Remote
Replication

16. In-region
Data Center
Primary Data Volumes
(Synchronous)
Hitachi
TrueCopy™
Synchronous
Remote
Replication
Primary Data Volumes
(Synchronous)
In-region
Recovery
Data Center

17. In-region
Data Center
JNLPrimary Data Volumes
(Synchronous)
Out of Region
Remote Data Center
JNL
Primary Data Volumes
(Asynchronous)JNLPrimary Data Volumes
(Synchronous)
Journal data transfers
Journal read requests
In-region
Recovery
Data Center
Hitachi
TrueCopy™
Synchronous
Remote
Replication
Hitachi
Universal
Replicator™
Asynchronous
Remote
Replication
Optional – Needed for Delta Resync

18. In-region
Data Center
Out of Region
Remote Data Center
JNL
Primary Data Volumes
(Asynchronous)JNLPrimary Data Volumes
(Synchronous)
Journal data transfers
Journal read requests
Out of Region
Remote Data Center
JNL
Primary Data Volumes
(Asynchronous)JNLPrimary Data Volumes
(Synchronous)
Journal data transfers
Journal read requests
In-region
Recovery
Data Center
Hitachi
TrueCopy™
Synchronous
Remote
Replication
Hitachi
Universal
Replicator™
Asynchronous
Remote
Replication

22. Enterprise

25. Technologie
zum Wohle
der
Gesellschaft
Namihei Odaira