Extreme Networks ExtremeWare XOS 10.1, Manual

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System Redundancy
ExtremeWare XOS 10.1 Concepts Guide 99
1
Relaying configuration information from the master to the backup
2 Ensuring that each individual process running on the system is in sync with the backup
3 Checkpointing any new state changes from the master to the backup
Relaying Configuration Information
This is the first level of checkpointing that is required to facilitate a failover: the primary’s configuration
information is transferred to the backup MSM, and the backup MSM ignores their own flash
configuration file.
When you initially boot the switch, the primary MSM configuration takes effect. During any standby
initialization, the primary’s saved configuration is copied to the local flash, and the current active
configuration is transferred to the backup processes. As you make configuration changes to the primary
MSM, they are relayed to the backup and incorporated into its configuration copy.
NOTE
To ensure that all of the configuration commands in the backup’s flash is updated, issue the
save
command after you make any changes.
If a failover occurs, the backup MSM continues to use the primary’s active configuration. If the backup
determines that it does not have the primary’s active configuration, it will use the configuration stored
in its flash memory.
NOTE
If you issue the
reboot
command before you save your configuration changes, the switch prompts you
to save your changes.
Synchronizing the Backup
The next step in checkpointing requires that the primary and backup configurations be in sync. Since
ExtremeWare XOS runs a series of processes (for example the device manager and the node manager), a
process starts checkpointing only after all the processes that it depends on have transferred their states
to the backup MSM.
After a process completes it checkpoints, this triggers the next process to proceed with its
checkpointing. You can also view the progress of the checkpointing. See the section “Viewing
Checkpoint Statistics” later in this chapter.
Relaying New State Information
The final step in checkpointing requires that any new configuration information or state changes that
occur on the master be immediately relayed to the backup. This ensures that the backup has the most
up to date and accurate configuration information.
Viewing Checkpoint Statistics
As previously noted, checkpointing is the process of copying the active state configurations from the
primary MSM to the backup MSM. Use the following command to view and check the status of one or
more processes being copied from the master to the backup MSM: