For a better file indexing and faster file search results you will have to go to CrushFTP root folder and there carefully not to brake the code edit the prefs.XML and set the "memcache" value to be true.

In admin, preferences, search config, configure a username for the search VFS location. This user just needs to have access to a root location that contains all files as its entire VFS will be cached in memory so any searches are now searching through this VFS for what the current user has access to. Set the search interval to something like 30 minutes for refreshes (it's kept updated on the fly for user changes through CrushFTP, but every 30 minutes re-scans the filesystem for anything changed outside of CrushFTP)

Speeds will be in about 1 second now to search the entire filesystem.