What is the NTDiskQuotaSidCache.ndx file for?

A customer was looking for information about the file %LOCAL­APP­DATA%\Microsoft\Windows NT\Disk­Quota\NT­Disk­Quota­Sid­Cache.ndx. All they could find is this KB article.

The NT­Disk­Quota­Sid­Cache.ndx file is used by the Disk Quota control panel. It’s a cache of SIDs and names, to improve performance of mapping SIDs to display names. You can delete it, and it will be regenerated the next time you run the Disk Quota control panel.

The customer never explained what they needed the information for, but they did thank us. (Or at least their liaison thanked us on the customer’s behalf.)