What the DDS service is

Hosted by a Storage Node, the Distributed Data Store (DDS) service interfaces with the Cassandra database to perform background tasks on the object metadata stored in the StorageGRID system.

Object counts

The DDS service tracks the total number of objects ingested into the StorageGRID system as well as the total number of objects ingested through each of the system’s supported interfaces (S3 or Swift).

You can see the Total Objects count on the Nodes page > Objects tab for any Storage Node.
DDS Overview page

Queries

You can identify the average time that it takes to run a query against the metadata store through the specific DDS service, the total number of successful queries, and the total number of queries that failed because of a timeout issue.

You might want to review query information to monitor the health of the metadata store, Cassandra, which impacts the system’s ingest and retrieval performance. For example, if the latency for an average query is slow and the number of failed queries due to timeouts is high, the metadata store might be encountering a higher load or performing another operation.

You can also view the total number of queries that failed because of consistency failures. Consistency level failures result from an insufficient number of available metadata stores at the time a query is performed through the specific DDS service.

You can use the Diagnostics page to obtain additional information on the current state of your grid. See the information on monitoring and troubleshooting StorageGRID.

Monitoring and troubleshooting StorageGRID

Consistency guarantees and controls

StorageGRID guarantees read-after-write consistency for newly created objects. Any GET operation following a successfully completed PUT operation will be able to read the newly written data. Overwrites of existing objects, metadata updates, and deletes remain eventually consistent.