anchor.diff:  The blob store uses the [Fog](http://fog.io/) Ruby gem such that it can use
   abstractions like Amazon S3 or an NFS-mounted file system for storage.
   
  -## <a id='nats'></a>NATS Messaging ##
  +##<a id='nats'></a>NATS Messaging ##
   
   The Cloud Controller interacts with other core components of the Cloud Foundry
   platform using the NATS message bus.
  
positive.code:   <li>Terminating and restarting half of the instances one by one.</li>
  </ul>
  
  ## <a id='database'></a>Database (CC_DB) ##
  
  The Cloud Controller database has been tested with Postgres.
  
  ## <a id='blob-store'></a>Blob Store ##
  
  The Cloud Controller manages a blob store for the following:
  
  
negative.code: 
  <strong><%= modified_date %></strong>
  
  The Cloud Controller provides REST API endpoints for clients to access the 
  system.
  The Cloud Controller maintains a database with tables for orgs, spaces, apps,
  services, service instances, user roles, and more.
  
  ##<a id='dea-placement'></a>Droplet Execution Agent (DEA) Placement Algorithm ##
  
  Whenever Cloud Foundry needs to spin up a new instance of an app, the Cloud Controller is responsible for [selecting a droplet execution agent (DEA) to run it](https://github.com/cloudfoundry/cloud_controller_ng/blob/2b1d38cba944086fa545d621a37ce4089b8e239e/lib/cloud_controller/dea/pool.rb#L44-L50).
  
  DEAs broadcast their availability to the Cloud Controller through a NATS message called an `advertisement`, which contains a `stats` hash with information about their available memory, available disk, the stack which the DEA runs, and an expiration time.
  
  The Cloud Controller collects these advertisements in a construct called a pool. When the Cloud Controller needs to find a DEA to run an app, it runs through the following steps, using criteria (minimum thresholds for disk, memory, etc.) specific to the app that the chosen DEA will run:
  
  1. It removes the expired DEA advertisements from the pool.
  1. It filters the remaining advertisements to include only those:
  