HA (Active/Standby)

NetLD has supported the High Availability (HA) Active/Standby feature since r20241218.0941.

HA provides system redundancy through paired primary (active) and standby servers. The primary server handles all monitoring and configuration operations, while the standby maintains real-time synchronization. Attached files are synchronized per 120 seconds with standby server.

HA uses active and standby as a roles.

For active server, NetLD manages devices or monitor devices.

For standby server, it receives transaction log (WAL) from active server and performs synchronization by recovering it.

Prerequisites

The HA feature uses eth1 to synchronize data because SSH is used, if there is a firewall between the active and standby servers, SSH communication from the standby server to the active server must be allowed. Also, the number of CPU cores, memory capacity, and disk size on both servers must be identical.

Restrictions

HA features have the following limitations. Please note that these features are not supported.

  • Simultaneous use with Smart Bridge
  • Using such as AWS and Azure in cloud environments
  • Taking over Syslog data received on the active server
  • Taking over system backup files obtained on the active server
  • Taking over the settings to be configured in the OVA console
  1. Confirm that the SSH Server is Running.

  1. Connect to the OVA console of the standby server.

  2. Press [5] (Admin Tools) > [7] (Setup replication) > [1] (Setup SSH host authentication) on the keyboard to configure SSH host authentication settings for the primary server.

  1. Enter the eth1 IP address of the primary server.

  1. Enter the password for SSH to the primary server.

  1. Press any key, such as the [Enter] key.

  1. Press [5] (Admin Tools) > [7] (Setup replication) > [2] (Toggle standby mode) on the keyboard to change the standby server from active to standby server role.

  1. Press [Y].

  1. Press [Y] to automatically restart the standby server.

Confirm Status

The status of HA feature can be checked from the OVA console screen.

  1. Connect to the OVA console of the primary server.

  2. Press [5] (Admin Tools) > [7] (Setup replication) > [3] (Monitor replication status) on the keyboard to check the status.

The status will be updated automatically when it is displayed. To close the status screen, press [Ctrl+C].

Once the HA configuration is set up, the backup phase is initiated first. During the backup phase, the initial data is copied from the primary server to the standby server.

Once the backup phase is complete, data streaming will begin. Once started, a screen similar to the one below will appear. After setting, confirm that “Replication state: streaming” is displayed.

Cases for Reconfiguration

In the following cases, the HA function must be configured again:

  • When restoring a system backup on the primary server
  • To restore the original state after failover.

Failover

Failover refers to the process of automatically switching to a redundant or standby system when the primary system fails, ensuring minimal downtime and continuous operation.

Manual Failover

To monitor on an active server, change the role from standby to active. The change procedure is as follows.

  1. Connect to the OVA console of the standby server.

  2. Press [5] (Admin Tools) > [7] (Setup replication) > [2] (Toggle standby mode) on the keyboard to change the standby server from standby to primary server role.

  1. Press [Y].

Press [Y] to automatically restart the standby server. After restarting, please log in from a web browser.

Auto Failover

When auto failover is enabled, the standby server will automatically change its role from standby to primary and take over monitoring if there is an unintended communication breakdown between the primary and standby servers for more than 60 seconds. If the user restarts/shuts down the primary server or successfully reconnects within 60 seconds, the switchover does not take place.

By default, auto failover is disabled. To have the standby server automatically take over monitoring if the primary server fails, follow these steps to enable auto failover.

  1. Connect to the OVA console of the standby server.

  2. Press [5] (Admin Tools) > [7] (Setup replication) > [4] (Toggle auto failover) on the keyboard to enable auto failover.

  1. After pressing [4] , the screen will automatically return to the first screen. Again, go to [5] (Admin Tools) > [7] (Setup replication) and confirm that the Toggle auto failover current is “enabled”.