Why is the Default partition so large?
8.x
If a log message does not match the criteria of any of the user-created partitions, it gets placed into the default partition.
Each partition is responsible for collecting and storing the logs for its retention policy. You can apply filters to each partition to define what logs to collect versus reject.
See vRealize Log Insight Index Partitions and Variable Retention Deep Dive
You can retain log data in a partition with a filter and a retention period. Index partitions let you define different retention periods for different types of logs. For example, logs with sensitive information might require a short retention period, such as five days. You can also archive the data in an index partition to an NFS mount, to retain the logs for an extended period.