Service Switchover
When a disaster occurs at the primary site, HyperReplication enables the secondary site to quickly take over services from the primary site to ensure service continuity.
HyperReplication 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:
- Before a disaster occurs, data in the primary LUN is consistent with that in the secondary LUN. If data in the secondary LUN is incomplete, services may fail to be switched.
- 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.
