When planning your SharePoint 2013 farm topology you need to plan for the Distributed Cache service. This feature provides in memory caching for features such as: newsfeeds, authentication, OneNote client access, security trimming and page load performance.
It’s important that you don’t run the Distributed Cache service on servers running SQL Server, Project Server, Excel Services and Search services. This is because these services require large amounts of memory and therefore compete with the Distributed Cache service for memory.
Don’t use Dynamic Memory with virtual machines in SharePoint 2013 as the cache memory allowance is calculated based on the total memory of the server and the cache isn’t automatically re-sized if more memory is added. Additionally, all servers running the Distributed Cache service must have exactly the same amount of memory. You can have a dedicated cache host, or run the service on multiple hosts in a cache cluster.
For more information on planning and configuring the Distributed Cache server see follow these links:
Manage the Distributed Cache service in SharePoint Server 2013
Plan and use the Distributed Cache service in SharePoint Server 2013
Richard Skinner 