Update configuring-playbook-synapse-s3-storage-provider.md

docs/configuring-playbook-synapse-s3-storage-provider.md

@@ -48,6 +48,8 @@ If you have existing files in Synapse's media repository (`/matrix/synapse/media
 - the existing files will remain on the local filesystem only until [migrating them to the S3 store](#migrating-your-existing-media-files-to-the-s3-store)
 - at some point (and periodically in the future), you can delete local files which have been uploaded to the S3 store already
 
+Regardless of whether you need to [Migrate your existing files to the S3 store](#migrating-your-existing-media-files-to-the-s3-store) or not, make sure you've familiarized yourself with [How it works?](#how-it-works) above and [Periodically cleaning up the local filesystem](#periodically-cleaning-up-the-local-filesystem) below.
+
 
 ## Migrating your existing media files to the S3 store