HP StoreOnce Backup - Manual (Page 169)

16 Failover
In this section:
•
What is failover? (page 169)
•
What happens during failover? (page 169)
•
What does the user need to do? (page 171)
•
Running failback (page 171)
What is failover?
Failover is when active software sessions fails on a node of a couplet within a cluster and are
moved and restarted on the other node within the couplet. All configured VTL devices, NAS shares,
replication mappings and StoreOnce Catalyst stores become available within 15 minutes of failing
on their original node. The Failover Status of the service set is shown on the HP StoreOnce page.
There are two types of failover – controlled and uncontrolled.
NOTE: Failover occurs only between nodes in a couplet and not between couplets in a cluster.
Controlled failover
A controlled failover is when the failing node is still able to actively manage active connections at
the point of failure. The node can complete a graceful shutdown of all the virtual devices running
on that node prior to being removed from use in a cluster.
A controlled failover is appropriate for some system maintenance instances, such as a maintenance
update to one of the hardware elements (for example, the storage controller). In this case, the
virtual devices on a failing node are able to cause known error or check conditions to be reported
to the backup application via the appropriate interface. When the service set from the failed node
is restarted on the paired node, the failed node’s power on checks will be quicker and simpler
because it was stopped in a controlled manner
Uncontrolled failover
An uncontrolled failover occurs when the active node suffers a rapid catastrophic hardware failure
or other trigger events that cause the active StoreOnce Management Console to power down the
failing node.
Some examples are:
•
The StoreOnce Management Console does not receive the Service Set node heartbeat.
•
The node server behaves as if powered off.
•
All of the node's internal network communications fail, leading to loss of heartbeat.
•
Software kernel panic, leading to loss of heartbeat.
•
Both SAS connections to the node’s local storage fail.
What happens during failover?
GUI and CLI
When the a node fails over and is not hosting the active StoreOnce Management Console, no
change occurs in the operation of the GUI or CLI.
What is failover? 169