High Availability - Draytek vigor3900 User Manual

The UPnP function dynamically adds port mappings on behalf of some UPnP-aware
applications. When the applications terminate abnormally, these mappings may not be
removed.
4 . 7 . 5 H i g h A v a i l a b
4 . 7 . 5 H i g h A v a i l a b
The High Availability (HA) feature refers to the awareness of component failure and the
availability of backup resources. The complexity of HA is determined by the availability
needs and the tolerance of system interruptions. Systems, provides nearly full-time
availability, typically have redundant hardware and software that make the system available
despite failures.
The high availability of the V3900 Series is designed to avoid single points-of-failure. When
failures occur, the failover process moves processing performed by the failed component (the
"Master") to the backup component (the "Slave"). This process remains system-wide
resources, recovers partial of failed transactions, and restores the system to normal within a
matter of microseconds.
Take the following picture as an example. The left V3900 Series is regarded as Master
device, the right V3900 Series is regarded as Slave device. When Master V3900 Series is
broken down, the Slave (backup) device could replace the Master role to take over all jobs as
soon as possible. However, once the original Master is working again, the Slave would be
changed to original role to stand by.
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256 Vigor3900 Series User's Guide