If your index is larger than the space on your hard drive allows, or you simply want to have a smaller, more manageable index, you can trim the amount of data in your index. Suggestions for trimming the index include:
*Edit the various Outlook Email data sources (Email, Contacts, Calendar, Task) to remove any folders that you might not really need to search. If you do not have Outlook Tasks or other Outlook items to index, you might consider setting those areas to Never Repeat the index.
*Edit the Files data source and remove any disks or folders that you're not likely to need to search. This includes especially the C:\ProgramData, C:\Program Files, C:\Program Files (x86), and C:\Windows directories, as well as the X1 Search data directory found in C:\Users\<username>\AppData\Local\X1 Search.
*If your Files indexing level is set to 'Everything (all files)' (the check-mark), consider switching to the next lower index level 'File names and sizes, plus content for specified extensions (specify below)' (the "glass 3/4 full") setting, or the 'File names, sizes and content only from specified extension (specify below)' (the "Sandwich") setting (green on top - white in the middle - green on bottom).
The 'Everything (all files)' setting performs full content indexing for all files X1 Search finds on the disk, oftentimes unnecessarily indexing files you'll likely never need to search (the internal content of an executable file or .dll, or a shortcut link file as an example).
Going with the "glass 3/4 full" setting still gives you full content indexing for the files active in our Global Whitelist Settings (see button with that name) and gives you Metadata indexing (file name, size, etc.) of files on the disk that are not set for content indexing.
If you don't care about searching the file types that are unchecked in our specified files list, try the "Sandwich" setting which focuses only on the selected file types and provides full content indexing for those file types.
Both the "glass 3/4 full" setting and the "Sandwich" setting leaves X1 Search very flexible in regards to your search usage while requiring a smaller and potentially more manageable index on your disk.