This article will provide steps to prevent out of control growth and steps perform when Indexes are growing larger than expected
Indexes can become much larger than needed when building in Normal mode (as compared to Bulk mode, which is used when rebuilding an index). Indexes should be much smaller than the Archive Store itself as it is only the search data for the email to be found. An Index as large as the Archive Store itself indicates that there is an issue with the content of the Index and a rebuild should be performed.
1. An Archive Store contains 100k emails and is 25GB in size
2. The index folder is also 25GB in size (this was build in Normal mode)
3. You rebuild the index (which utilizes Bulk mode) and resulting index is only 5GB in size The important fact here is, that the index is significantly smaller in size after rebuilding it.
Set Indexing Interval
To help prevent the issue from occurring in the future, follow the steps in Configuring Search Index Schedule as defined below.
Set the Indexing Interval (Configuration > Archive Stores > Index Management) to occur every 2 hours, 4 hours or a higher value (the higher the value the better in regard of this topic)
NOTE: Keep in mind the higher this value is set, the longer it will take for any new mails to be Index and available in Search. Users can still find new mail in the Archiver Console > Archive tab without the Search.
To reduce the size of existing large indexes follow the steps in Rebuilding an Archive Store Index.