Size of the Confluence index is extremely large due to Usage Tracking Plugin
The size of index directory grows rapidly after few days of use. For example, you may discover an increase over 1 GB in size over 7 days of usage.
Rapid index file size increase can be caused by the usage tracking plugin, this plugin is known to cause performance problems and has been disabled by default since Confluence 3.0, Atlassian strongly advises against enabling it on large instances.. See USGTRK-15 for futher information.
- Disable the usage tracking plugin.
- Follow the instructions at How to Rebuild the Content Indexes From Scratch on Confluence Server