Huawei OceanStor V3 Series Features Manual page 22

OceanStor V3 Series
Remote Replication Feature Guide for Block
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Choose the 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:
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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, the administrator needs to manually
change the access permission of secondary LUNs to accessible to enable a service switchover.
Figure 1-4
Issue 06 (2018-01-30)
The maximum acceptable amount of time prior to a disaster wherein changes to data may
be lost. Data changes preceding the disaster by longer than this amount of time are
preserved via recovery. Synchronous remote replication copies data from a primary LUN
to a secondary LUN in real time, ensuring that the Recovery Point Objective (RPO) is 0.
Zero is a valid value and meets the "zero data loss" requirement. A remote disaster
recovery system built based on synchronous remote replication implements data-level
disaster recovery with a high disaster recovery level (tier 6—zero data loss). In
asynchronous remote replication scenarios, the RPO is the time that you set for Interval.
RTO
The maximum acceptable amount of time required to return one or more applications
and associated data to a normal operational state after a disaster. The indicated recovery
time serves as the objective and ensures that the standby host takes over services as
quickly as possible. The Recovery Time Objective (RTO) depends on host services and
disasters in remote replication scenarios.
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.
shows how a service switchover is implemented through remote replication.
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