3PAR Remote Copy

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3PAR replication software is known as Remote Copy. Below are some notes that describes Remote Copy. Efficiencies in the initial copy creation of the target volumes that do not require replication of “zero” data across the replication network (regardless of target volume type, thick or thin) result in a faster initial synchronization and better network utilization.

Implemented over a native IP network (through the built-in Gigabit Ethernet interface available on all nodes) and native Fibre Channel, users may flexibly choose one of four different data replication modes—Asynchronous Streaming or Asynchronous Periodic (for asynchronous replication), Synchronous, or Synchronous Long Distance.

Asynchronous Streaming is not support on the built-in GiGe interface at the release of HPE 3PAR OS version 3.2.2.

A bit more about 4 types of replication mode:
Async Streaming: RPO in seconds. It is suitable for customers that want near zero RPO without the additional host latency associated with the synchronous mode of replication.
Async Periodic: Changed data within an HPE 3PAR Remote Copy Volume Group is transferred only once—no matter how many times it may have changed—between synchronization intervals. Gives RPO in minutes over extended distances.
Synchronous: Suitable for data centers within metro distances and have a recovery point objective of zero seconds. When combined with HPE 3PAR Peer Persistence these solutions also enables recovery time objective that can be measured in seconds.
Synchronous Long Distance: It delivers a disaster recovery solution across long distances with a potential for zero data loss RPO and an RTO of minutes. This is achieved with a replication configuration that uses three sites to simultaneously replicate a virtual volume from the primary array in synchronous mode to a target array located at a synchronous site (within a metropolitan area) and in asynchronous periodic mode to a target array located at an asynchronous site (across a long distance). In addition to the HPE 3PAR Remote Copy connections from the primary array to the two backup arrays, a passive asynchronous periodic link is configured from the synchronous target array to the disaster recovery target array. Under the Synchronous Long Distance mode algorithm, the synchronous target array intelligently tracks the delta set of I/Os that have been acknowledged to the host but which have not yet been replicated to the asynchronous target array. In the event that a disaster takes the primary storage array down, the user has the flexibility to recover either from the synchronous target array or the asynchronous target array.

Choice of connectivity: FC, FCIP, RCIP
Replication Modes: Synch, Async (Periodic, Streaming), Sync Long Distance
Topology: 1-1, Many to one, One to Many
Failover Procedures: Stop, Failover, Recover (remote site will become RW, source will become RO, replication will reverse), Restore (will go back to original state)

Before you can failover, you have to “Stop RCG”. Once that’s run, you run “Failover RCG”.

After Failover stage, there are two options – Revert Failover RCG, Recover RCG.

Revert Failover is used in case where data on primary needs to be retained, and data on backup can be overwritten. VV will become RW on Primary and RO on target. All deltas on backup system will be wiped out. After this step, you can either “Start RCG” to resume the replication from source to target or “failover” again to the previous failed over state.

Recover RCG option initiates reverse replication from target to source, and synchronises the delta changes from the backup system to the primary. After its execution, the role of RCG on source becomes secondary-Rev. VV on source becomes NR.

First perform “Failover”, then “Recover”, now if you run “Restore”, it will restore replication to a pre-failover state after the Recover operation was completed. Source RCG will be “Primary” and Backup RCG will be “Secondary”. Source volumes become RW, and target volumes become RO.

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sanaswati
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