HP StorageWorks Storage Mirroring Evaluation Guide (T2558-96326, April 2009)

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Failure monitoring and failover
Failover is the process in which a target stands in for a failed source. As a result, user and application
requests that are directed to the failed source are routed to the target.
Storage Mirroring monitors the source status by tracking network requests and responses exchanged
between the source and target. When a monitored source misses a user-defined number of requests,
Storage Mirroring assumes that the server has failed. Storage Mirroring then prompts the network
administrator to initiate failover, or, if configured, it occurs automatically.
The failover target assumes the network identity of the failed source. When the target assumes the
identity of the source, user and application requests destined for the source server or its IP
address(es) are routed to the target.
When partnered with the Storage Mirroring data replication capabilities, failover routes user and
application requests with minimal disruption and little or no data loss. In some cases, failover may
be used without data replication to ensure high availability on a server that only provides processing
services, such as a web server.
Source Target
User and application requests
sent to the source name or IP address
Mirroring and replicating data
Failure monitoring
Before failover occurs
Source Target
User and application requests
sent to the source name or IP address
After failover occurs
which is now running o the target
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