Continuity Engine Troubleshooting - Synchronization Failures

Continuity Engine Troubleshooting - Synchronization Failures

Neverfail Continuity Engine provides protection to your applications by replicating data to a passive server. Continuity Engine attempts to synchronize protected data on all servers and continually replicates changes to that data.
This article discusses the symptoms, causes, and resolutions when Continuity Engine is unable to synchronize data.
Synchronization Failures

Learning objectives 

At the completion of the session you should be able to:
  1. Identify symptoms of synchronization failures.
  2. Identify causes of synchronization failures.
  3. Recall resolutions to synchronization failures. 

Overview

When Neverfail Continuity Engine starts or is restarted, it performs a Full System Check and synchronizes protected data between the active and passive servers. 
Synchronization must complete before you can switch server roles (make active) or before you can be confident that the passive servers has a true copy of the protected data from the active server.

Symptoms

During the synchronization process, Neverfail Continuity Engine checks to ensure that protected data on the passive server(s) is identical to protect the data on the active server. If Continuity Engine can't access protected files during the Full System Check, it marks the file as out of sync, adds an error entry in the log file, and continues. Continuity Engine also displays an out-of-sync status in the never fail Advanced Management Client.

Causes

Failure to synchronize can be caused by a variety of problems. The following are the most common. 
  1. Neverfail Continuity Engine may fail to synchronize if protected files are in use on a passive server. This can be caused by:
    1. A service is running on the passive server.
    2. Other applications accessing the protected file.
    3. Improperly created file filters. 
  2. Other problems that may cause synchronization failure can include:
    1. Misconfigured channel.
    2. Misconfigured disks.
    3. Registry security issues.
    4. Unprotected file features.
    5. Insufficient disk space on the servers.
    6. Inadequate hardware or other system resources.
    7. Misconfiguration of the Continuity Engine software.
  3. Finally, using hardware that doesn't meet Continuity Engine’s minimum requirements may cause MaxDiskUsage errors or channel drops, which may also result in the failure of the Full System Check.

Resolutions

Should you experience the synchronization failure, take the following actions to correct the problem:
  1. Check that there are no services or applications running on the passive server that would prevent write access to protected files.
  2. Verify that you excluded application database files and Neverfail Continuity Engine temporary files from the file-level Anti-Virus scanning on all servers.
  3. Check to ensure that the active and passive servers can communicate across the Neverfail Channel.
  4. Verify that the Send and Receive queues have not exceeded the configured size limits.
  5. Check that all protected files on the active server are accessible and do not contain unsupported or extended features. 
If the servers are significantly different in hardware specifications, the one with the lower specification should be run as the active server for a period to ensure that it is adequately powered for the purpose. Remember that Continuity Engine is symmetrical in almost all respects, and it doesn't matter whether the Primary, Secondary or even Tertiary is normally the active server.

Following Neverfail Continuity Engine’s installation and configuration process and using the hardware that meets or exceeds the minimum requirements will ensure that your Continuity Engine system synchronizes and functions properly.

Wrap Up

This article discussed problems that you may encounter during the Neverfail Continuity Engine Synchronization Process including:
  1. Protected files being accessed by other applications on a passive server.
  2. A misconfigured channel. 
  3. Unsupported file features.
  4. insufficient disk space.
  5. MaxDiskUsage errors and channel drops due to inadequate hardware. 
  6. This session also covered how to troubleshoot synchronization failures and how to prevent them.

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