Spectra Logic Spectra T950V User Manual page 68

Chapter 2 — Architecture Overview
Figure 25 shows a simplified view of how the failover pair operates. Port A
on each controller in the pair is connected to the same Fibre Channel
switch. Both ports have the same configuration, except that the primary
operates in target mode and the secondary is not active.
The two controllers use the library's internal communication bus to
monitor each other and to maintain a cache of the library's inventory
database.
A failover event occurs when the secondary controller detects that the
primary controller is no longer communicating on the library's internal
communication bus. After sending a query to the primary controller to
confirm that it is no longer communicating, the secondary controller takes
over the exact configuration of the primary controller and begins receiving
and processing the media changer commands sent from the host.
Only the secondary controller (acting as primary) is functional after the failover. A
Important
failure on this controller disrupts communications with the hosts. Troubleshoot the
cause of the failover and reconfigure Controller Failover as soon as possible.
BlueScale Controller Failover allows backups to continue in the event that
library communication to the primary controller is disrupted. Because both
controllers are connected to the same Fibre Channel switch and maintain a
synchronized image of the library's inventory database, the failover occurs
without manual intervention. You can then troubleshoot the failed
controller at your convenience.
August 2019
SAN
SAN
Robotic control path (target port)
Internal communication bus (mirror inventory & partner monitor)
Figure 25 Paired controllers configured to provide failover
redundancy.
High-Availability Configurations
Primary Controller
Secondary Controller
Before failover
A
Primary Controller
B
A
Secondary Controller
B
After failover
User Guide—Spectra T950V Library
68