Enabling Persistence (Preview)

By default, Anzo manages the data in AnzoGraph by automatically reloading Graphmart data into memory when AnzoGraph is restarted. You also have the option to enable persistence on the AnzoGraph instance. When persistence is enabled, AnzoGraph saves the data in memory to disk after every transaction. Each time AnzoGraph is restarted, the persisted data is automatically loaded back into memory. Once the data is loaded into memory, rather than automatically reloading active Graphmarts, Anzo checks to see if the last updated timestamp in AnzoGraph matches the last updated value in Anzo. If the timestamps match, Anzo does not initiate a reload. If there is a mismatch, Anzo reloads the active Graphmarts to update the data in memory to the latest version.

This topic lists important information to consider before enabling persistence and provides instructions for enabling persistence in the AnzoGraph configuration file.

Important Considerations

Before enabling persistence, consider the following important notes:

• In general, each AnzoGraph server needs access to about twice as much disk space as RAM on the server. By default, AnzoGraph saves data to the <install_path>/persistence directory on the local file system. You can also configure AnzoGraph to save data to a mounted file system. For more information, see Relocating AnzoGraph Directories.
• Persisted data is unique to each AnzoGraph version and cannot be re-used after an upgrade. If you upgrade AnzoGraph and persistence is enabled, the database will not start until it is reinitialized to remove the persisted data. See Reinitialize the Database for instructions.
• When persistence is enabled, transactional workloads that perform many concurrent write operations may experience a performance degradation due to the overhead of writing the data from each transaction to disk.

Enabling Persistence

Follow the steps below to enable the AnzoGraph save to disk option.

1. Stop the database. See Stop the Database (Leave the System Management Daemon Running) for instructions.
2. On the leader node, open the AnzoGraph settings file, settings.conf, in a text editor. The file is in the <install_path>/config directory.
3. In settings.conf, find the following line in the file:

   enable_persistence=false

4. Change the enable_persistence value to true:

   enable_persistence=true

5. Save and close settings.conf.
6. Restart the database to apply the configuration change. See Start the Database (the Daemon is Running) for instructions.

After each transaction, AnzoGraph saves the data in memory to disk in the location specified in the persistence_directory setting. Each time AnzoGraph is restarted, the persisted data is automatically loaded back into memory.