DOCS-656 GridFS FAQ review edits

Author: Bob Grabar

source/faq/developers.txt

@@ -151,43 +151,45 @@ flag to modify the file preallocation strategy.
 
 .. seealso:: This wiki page that address :wiki:`MongoDB disk use <Excessive+Disk+Space>`.
 
-When should and shouldn't I use GridFS?
----------------------------------------
+.. _faq-developers-when-to-use-gridfs:
+
+When should I use GridFS?
+-------------------------
+
+For documents in a MongoDB collection, you should always use
+:term:`GridFS` for storing files larger than 16 MB.
+
+For files on your file system, storing the files in a MongoDB database
+through GridFS provides advantages in a number of situations:
 
-:term:`GridFS` is a specification for storing and retrieving files
-that exceed the :term:`BSON`-document :ref:`size limit
-<limit-bson-document-size>` of 16MB. You should always use GridFS
-for storing files larger than 16MB.
+- If your file system limits the number of files in a directory, you can
+  use GridFS to store as many files as needed in a directory.
 
-Additionally, GridFS storage has advantages in the following other
-situations as well:
+- When you want to store file metadata (such as description, download
+  count, and MD5 hash) together with the file itself. GridFS stores file
+  metadata in the same bucket as the file's content.
 
-- When you have many thousands of files, GridFS tends to handle the
-  large numbers better than many file systems.
+- When you want to keep your files and metadata automatically backed up.
+  If you set up replication, MongoDB makes automatic backups of your
+  files and metadata.
 
-- When users frequently upload files. When users upload files you tend
-  to have a lot of files, all of which are also usually replicated and
-  backed up. GridFS lets you manage them the same way you that you
-  manage your data. You can query the files, for example by user or
-  upload date, directly in the file store, without a layer of
-  indirection.
+- When you want to access information from random sections of large
+  files without having to load whole files into memory. GridFS lets you
+  access sections of files without having to read the entire file, for
+  example skipping into the middle of a video.
 
-- When files often change. If you have certain files that change a lot,
-  consider storing them in GridFS, which then allows you to modify them
-  in one place. Also, all clients get the updates. If you instead store
-  in source tree, you must deploy an application to update files.
+Do not use GridFS if a file is under the 16 MB limit and you need to
+update the file atomically. Instead, consider either:
 
-There are some situations where you should not use GridFS:
+- Storing the file manually within a single document. This can be
+  accomplished using the BSON BinData datatype. For details on using
+  BinData, see the :doc:`drivers </applications/drivers>` documentation
+  for your driver.
 
-- When you have only a few small and static files, such as js, css, and
-  images on a web site.
+- Storing multiple versions and specifying which version is current.
+  This can be changed atomically after the new file is uploaded.
 
-.. todo Verify that this info from the wiki can be deleted:
-   Note that if you need to update a binary object atomically, and the
-   object is under the document size limit for your version of MongoDB
-   (16MB for 1.8), then you might consider storing the object manually
-   within a single document. This can be accomplished using the BSON
-   bindata type. Check your driver's docs for details on using this type
+For more information on GridFS, see :doc:`/applications/gridfs`.
 
 How does MongoDB address SQL or Query injection?
 ------------------------------------------------