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Swarm calculates storage use by addressable object in order to support conventional (storage filer) reporting of file counts and their space usage. This approach tracks cluster-wide capacity by counting logical objects (the unique content of uploaded and versioned files) rather than actual streams (the raw space that is consumed by all Swarm components, including replicas, EC segments, context objects, and manifests). For example, if your The versions add to the object totals; if a cluster held just one 20 MB image with 3 replicas and 4 prior versions, only the versions would add to the object totals: 5 logical objects and ~100 MB logical space is consumed.
Swarm continuously sends its nodes updates about the cluster's logical usage (the current number of objects and the space they consume), which the nodes update with their own space-affecting activity. Swarm then aggregates these updates (for accuracy) and publishes them via SNMP and REST as logicalObjects and logicalSpace. A third statistic, logicalUnprocessed, exists to provide insight into the accuracy of the other statistics (the closer to zero it is, the more accurate they are). Swarm propagates this data quickly, so there is little lag behind the cluster activity that affects usage: writes, deletes, and updates. After a disk failure, however, you will see a drop in the aggregated estimates, followed by an increase to the true value, once Volume Recovery recreates the lost streams that were on that disk.
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