How to Resolve two active servers

How to Resolve two active servers


Symptoms

The occurrence of two active servers is not by design and, when detected, should be resolved immediately. When two identical active servers are live on the same network, VMware refers it as Split-brain syndrome.

Split-brain syndrome symptoms:

  • Both servers are running and in an active state. This is visible on the Taskbar icon as P / A (Primary and active) and S / A (Secondary and active).
  • An IP address conflict might be detected on a server pair running vCenter Server Heartbeat on the Principal (Public) IP address.
  • A name conflict might be detected on a server pair running vCenter Server Heartbeat. Typically, in a WAN environment, the Primary and Secondary servers connect to the network using different IP addresses. As a result, no IP address conflict occurs. However, if the servers are running with the same name then a name conflict may result. This only happens if both servers are visible to each other across the WAN.
  • Clients cannot connect to the server running vCenter Server Heartbeat.

Purpose

This article provides information about the symptoms and resolutions for two active servers.

Resolution

The most common causes of two active servers (Split-brain syndrome):

  • Loss of the VMware Channel connection (most common in a WAN environment).
  • The active server is too busy to respond to heartbeats.
  • Misconfiguration of vCenter Server Heartbeat software.

It is important to identify the cause of Split-brain syndrome and resolve it to prevent this issue from reoccurring.

When Split-brain syndrome occurs, the server with the most up-to-date data must be identified.

Note: If the wrong server is identified, it can result in data loss. Care should be taken to reinstate the correct server.

The following can help identify the server with the most up-to-date data:

  1. Check the date and time of files on both servers. The most up-to-date server will be made the active server.
  2. From a client PC on a LAN, run 'nbtstat -A 192.168.1.1' where the IP address should be the principal (public) IP address of your server. This can help identify the MAC address of the server currently visible to client machines.

Note: If both active servers have been servicing clients, perhaps at different WAN locations, only one server can be made active. Both servers contain recent data, which cannot be merged using vCenter Server Heartbeat. One server must be made active and one server passive to restart replication. Once replication is restarted, all data on the passive server is overwritten by the data on the active server. It may be possible to extract the up-to-date data manually from the passive server prior to restarting replication. Consult the Microsoft Knowledge Base for information regarding tools that can be used for this purpose. For additional information, please contact VMware Support.

To resolve two active servers:

  1. Identify the server with the most up-to-date data or the server you want to make active.
  2. Shutdown vCenter Server Heartbeat on both servers (if it is running).
  3. On the server you want to make passive, right-click the Taskbar icon, and select Server Configuration wizard.
  4. Select the Machine tab and set the server role to passive. Do not change the Identity of the server.
  5. Click Finish and reboot this server.
  6. Start vCenter Server Heartbeat (if required) and verify that the Taskbar icon reflects P / - (Primary and Passive) or S / - (Secondary and Passive).
  7. On the active server, right-click the Taskbar icon and select Server Configuration wizard.
  8. Select the Machine tab and verify the server role is set to active. Do not change the Identity of the server.
  9. Click Finish and reboot this server. As the server restarts, it connects to the passive server and starts replication. Data on the passive server is overwritten by data on the active server.
  10. Start vCenter Server Heartbeat (if required) and verify that the Taskbar icon reflects P / A (Primary and active) or S / A (Secondary and active).
  11. Log in to the vCenter Server Heartbeat Console.
  12. Verify that the servers have connected and replication has started.
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