Re: /vastorage .fdt files
These files are basically the index and should not be deleted.
The size of the index is greatly influenced by the amount of files / data that is being exposed over Filr, the amount of users in Filr, and last but not least, whether contents indexing is enabled.
With that last one enabled the index' size might grow to a 10fold compared to a Filr setup where contents indexing is not enabled.
Enabling contents indexing (allowing Filr users to search for files based on it's contents) should be considered with care and only enabled when it is required, as Filr users can search for files based on their name even when contents indexing is not enabled.