Recovery Options for Shared Nothing Persistence

You can use the five new policies for the shared nothing persistence as recovery options.

The be.engine.cluster.recovery.distributed.strategy parameter is now also supported for the shared nothing persistence. There are five new recovery policies added as part of the recovery options. When shared nothing persistence is implemented and recovery is issued, then the policy determines how and when the recovery can be made. The default value of the property is no_data_loss.

Policy Policy Description
no_data Recovers the space without any data. This is same as removing shared nothing persistence files.
data_loss Recovers the space with available data from each seeder. If recovery is done with missing seeders, there is a potential for data loss, because not all members are started, to ensure that all data is recovered. This policy ensures best-effort recovery with the available data.
no_data_loss (Default). Recovers the space only if there are enough members to be able to recover the previous state of the cluster. Otherwise recovery throws an exception.
fast_load_only Recovers the space only if all of the members that were active before the shutdown are available in the cluster. If there are more or less cluster members than before the shutdown, recovery throws an exception.

When the fast_load_only is used; it is advisable to set 'Cache Agent Quorum' to the total number of cache nodes. This increases the chances of a succesful recovery.

robost_load_only Forces slow recovery.

The be.engine.cluster.as.minSeeders property's value is the Cache Agent Quorum value minus the number of backup copies. Starting with this release, the seeder information (the current seeder list) is stored in the shared nothing persistence files during shutdown. This information is then used during startup or restart to perform recovery. If cluster is exactly the same during startup (that is, exactly the same members are available and quorum is satisfied), then fast loading of the data is performed.