Most of the new features and capabilities in Volt V8.0 do not impact existing applications. However, there are a few changes that do require minor changes to the configuration when upgrading from earlier versions. Existing customers should take note of of the following changes:
Change to default Kafka versions for import
For the kafka import connector and the kafkaloader command line utility, the default Kafka
        version has changed from 0.8.2 to 0.10.2 or later. For customers already using Kafka 0.10.2 or later, there are no
        changes needed to their configuration, scripts, or applications. For customers who wish to continue using the older
        Kafka version 0.8.2, they will need to add the attribute version="8" to the import
        connector configuration and/or use the command line utility kafkaloader8 instead of the default
        kafkaloader.
The "elastic" attribute removed from <cluster>
An artifact of an old feature provided for backwards compatibility, the elastic attribute of the <cluster> element in the
        configuration file was disabled and deprecated several years ago. It has now been removed. Although it is unlikely any
        still exist, configuration files that do include this attribute will now fail to parse. Simply remove the attribute and
        try again.
The <consistency> element removed from the configuration file
The <consistency> element was recently deprecated, since "fast" read
        consistency no longer provides any significant performance improvement over "safe" mode but does introduce potential
        risks during failure scenarios. It has now been removed from the allowable configuration file syntax. If you included
        <consistency> in your configuration file, please remove it before starting a
        Volt 8.0 cluster.
Old commands for starting Volt are no longer supported
Volt 6.6 introduced two new integrated commands, init and start, for
        starting Volt servers. At that time the old commands (add, create,
        recover, and rejoin) were deprecated. The old commands have now been removed from
        the product. If you still use the older commands, please update your scripts to use the new commands as described in the
        chapter "Starting the Database" in the
        Using VoltDB manual.