final draft with milkie's changes to line 80

Author: barriesegal

draft/faq/storage.txt

@@ -76,6 +76,8 @@ uses in the course of normal operation. Often this is a subset of the
 total data size, but the specific size of the working set depends on
 actual moment-to-moment use of the database.
 
+If you run a query that requires MongoDB to scan every document in a collection, the working set will expand to include every document. Depending on physical memory size, this may cause working set documents in other collections to be ejected from physical memory. The next time such documents are accessed, a hard page fault may be incurred. 
+
 If you run a query that requires MongoDB to scan every
 :term:`document` in a collection, the working set includes every active
 document in memory.