Summary

This Knowledgebase article describes the functionality and configuration of the Fast Check feature available starting with Neverfail Heartbeat version 6.5.

More Information

Fast Check is an enhancement of the Full System Check verification process and may reduce verification times considerably if the following runtime conditions are met:

• The application services must not have been started prior to starting replication.
• A file must have been verified and or synchronized conventionally at least once. 

In comparison to standard verification which compares checksums of the protected file data during a Full System Check, Fast Check compares the file properties; file attributes, file length, security descriptor, and file times of the protected files during a Full System Check. If any of these file properties are found to be different for a particular file, then the file is verified using standard verification procedures. If the file properties are found to be the same then the file is considered to be the same and no further processing is carried out.

A Fast Check enhanced Full System Check is intended to minimize the resynchronization time after restarting replication by reducing the time taken during a Full System Check to verify the files and can help in situations such as after server reboots. The greatest benefits from Fast Check will be experienced when the protected files are in-sync after restarting replication, for example if half the files are in-sync and half are not then Fast Check will quickly check the in-sync files while the out-of-sync files will be subjected to standard verification. Fast Check enhanced Full System Checks were designed to work in conjunction with the Controlled Shutdown mechanism to allow for after hours unattended server reboots for maintenance purposes.

Configuring Fast Check

The Fast Check functionality is enabled by default at Neverfail Heartbeat install time. It can be enabled / disabled from the Neverfail Heartbeat Management Client Data: Replication> Configure button in the top right corner of the page.

The Maximum Application Delay field specifies how long the Protected Application startup may be delayed before starting replication. It is mandatory for replication to start before the application services are started to ensure that all changes to the file system are captured within the Fast Check mechanism. If the timeout is exceeded, the Protected Application will start prior to replication starting and when replication is started, the Full System Check will not include Fast Check.

Fast Check limitations

• Alternate Data Streams (ADS) cannot be Fast Checked; they will always undergo regular verification
• Fast Check is limited to a maximum number of 1 million files

Applies To

Neverfail Continuity Engine

Related Information

None

KBID-2295