Additions to strage and migration

docs/usage/migration.rst

@@ -18,14 +18,15 @@ When we create a bucket we need to provide a Location, otherwise the default
 one is used.
 
 .. note::
-    Before migrating our models, we need to transfer the actual files in the
-    new storage with the new location. Then we can just bulk update our
-    FileInstance objects pointing to the new bucket.
+    Before updating our records to point to the new :code:`Location`, we need
+    to copy the actual files in the new storage with the new location.
+    Then we can just bulk update our FileInstance objects pointing to the new
+    bucket.
 
 There is a task :code:`invenio_files_rest.tasks.migrate_file`
-which is used to migrate a file instance to a new location. A new location
+which is used to migrate a :code:`FileInstance` to a new location. A new location
 might be in remote system on a different bucket, even on a different storage
 backend. If the process does not complete successfully then the destination
-FileInstance is removed completely. The task also accepts an argument
+:code:`FileInstance` is removed completely. The task also accepts an argument
 :code:`post_fixity_check` which enables the file checksum verification after
 the operation is complete.

docs/usage/storage_backends.rst

@@ -10,16 +10,25 @@ Storage Backends
 In order to get started we need to setup and configure a storage backend.
 Storage will serve as an interface for the actual file access.
 
-In the configuration of the application, we can set the path of the factory that we want to use in order to create a storage instance.
-Each file instance uses the storage factory to create a storage interface for itself.
+In the configuration of the application, we can set the path of the factory
+that we want to use in order to create a storage instance. Each file instance
+uses the storage factory to create a storage interface for itself.
+
+Under the hood the module uses `PyFilesystem <https://www.pyfilesystem.org/>`_
+to save files. This file system abstraction gives us the flexibility to be able
+to swap storages very easy. The storage backend can also be a cloud service, as
+an example you can have a look at
+`invenio-s3 <https://invenio-s3.readthedocs.io/>`_ which offers integration with
+any S3 REST API compatible object storage.
+
 
 Build your own Storage Backend
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Advanced topic on how to implement and connect your own storage Backend for
 invenio-files-rest.
 
-In order to use a different storage backend, we just need to subclass the FileStorage class,
-and provide implementations for some of the methods, as follows:
+In order to use a different storage backend, we just need to subclass the
+FileStorage class, and provide implementations for some of the methods, as follows:
 
 Mandatory methods to implement:
 
@@ -37,3 +46,4 @@ Optional methods to implement:
 * :code:`_init_hash`
 * :code:`_compute_checksum`
 * :code:`_write_stream`
+