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HyperReplication Feature Guide for Block

OceanStor V5 Series V500R007

This document is applicable to OceanStor 5110 V5, 5110F V5, 5300 V5, 5300F V5, 5500 V5, 5500F V5, 5600 V5, 5600F V5, 5800 V5, 5800F V5, 6800 V5, 6800F V5, 18500 V5, 18500F V5, 18800 V5, and 18800F V5. It describes the working principle and application scenarios of the HyperReplication feature (for block). Also, it explains how to configure and manage the feature.
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Service Switchover

Service Switchover

When a disaster occurs at the primary site, the remote replication feature enables the secondary site to quickly take over services from the primary site to ensure service continuity.

The remote replication feature not only implements remote data backup but also recovers services as soon as possible in the event of a disaster to keep service continuity. The following two indicators need to be considered before a service switchover:

  • Recovery Point Objective (RPO)

    The maximum acceptable time period prior to a failure or disaster during which changes to data may be lost as a consequence of recovery. Data changes preceding the failure or disaster by at least this time period are preserved by recovery. Synchronous remote replication copies data from a primary LUN to a secondary LUN in real time, ensuring that the RPO is zero. Zero is a valid value and is equivalent to a "zero data loss" requirement. A remote DR system built based on synchronous remote replication implements data-level DR. In asynchronous remote replication scenarios, the RPO is the time period that you set for the synchronization interval.

  • Recovery Time Objective (RTO)

    The maximum acceptable time period required to bring one or more applications and associated data back from an outage to a correct operational state. The indicated recovery time serves as the objective and ensures that the standby host takes over services as quickly as possible. RTO depends on host services and disasters in remote replication scenarios.

Choose a remote replication mode based on the RPO and RTO requirements of users.

Service Switchover Through Remote Replication

Services can run on the secondary storage system only when the following conditions are met:

  • Historical service data exists in the secondary storage system.
  • Services on the production host have also been configured on the standby host.
  • The secondary storage system allows a host to access a LUN in a LUN group mapped to the host.

When a disaster occurs at the primary site, the remote replication links between the primary LUN and the secondary LUN go down. If this occurs, an administrator needs to manually change the access permission of the secondary LUN to writable to enable a service switchover. Figure 1-4 shows how a service switchover is implemented through remote replication.

Figure 1-4 Service switchover through remote replication
NOTE:

After a primary/secondary switchover, the primary and secondary sites record changed data to avoid full synchronization when the secondary site becomes the primary site.

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Updated: 2019-07-11

Document ID: EDOC1000181492

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