Sharepoint 2013-Minimal Download Strategy.(MDS) &DCS

You might seen the page URL in sharepoint 2013 looks like below.

http://sp201323:8085/sites/TeamSite/_layouts/15/start.aspx#SitePages/Home.aspx
In the above URL, you are looking for home.aspx to load.But the URL targets start.aspx.Do you know what is the reason behind this?
This is nothing but Minimal Download Strategy Feature.Minimal Download Strategy (MDS) is a new technology in SharePoint 2013 that reduces the amount of data that the browser has to download when users navigate from one page to another in a SharePoint site.

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Minimal Download Strategy : MDS is a feature provided by SharePoint 2013 to improve the page load that reduces the amount of data that the browser has to download when users navigate from one page to another compatible page in a SharePoint site. When users browse an MDS-enabled site, the client processes only the differences (or delta) between the current page and the requested page.

Minimal Download Strategy implements a new download manager that interfaces between the client and server and retrieves the data as needed depending the initiating request. Each control on the page uses the download manager to update itself when necessary.

Enable Minimal Download Strategy

SharePoint 2013 introduces a new feature called Minimal Download Strategy which is used to improve the performance and reduces the amount of data that the browser has to download when users navigate from one page to another in a SharePoint site. This can be activated in a site by either of the following ways

•     Activate the web scoped feature – Minimal Download Strategy feature
•     Using Server Side Object Model
•     Client Side Object Model
•     Power Shell

In this blog you will see how to enable Minimal Download Strategy for a site using Power Shell Script. Open SharePoint 2013 Management Shell as an administrator and run the following script.

$web=Get-SPWeb "http://c4968397007"

$web.EnableMinimalDownload=$true;

$web.Update();

Benefits of using MDS

Using MDS provides several benefits, including:

• Speed: 
• Smooth transitions:
• Browser navigation controls: Other AJAX-based systems confuse the previous and next buttons in browsers. Because MDS updates the URL in the browser window, the previous and next buttons work just as they are supposed to.
• Backward compatibility: The MDS engine either provides MDS navigation immediately or detects when it isn’t possible. In the case where MDS navigation isn’t possible, a full page load occurs instead. This process is called failover.

MDS architecture

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The basic mechanics of MDS are pretty simple. The main components of MDS are two engines, one in the server and another in the client, that work together to calculate the changes and render the pages in the browser when the user navigates from page to page in the site.

Figure: MDS flow when a user navigates the site

1. The browser requests the changes between the current page and a new one in the SharePoint site.
2. The MDS engine in the server calculates the delta between the current and the new pages.
3. The MDS engine in the server sends the delta to the MDS engine in the client.
4. The MDS engine in the client replaces the changed areas on the current page with the new page content.

Limitations

The MDS is not enabled on publishing sites and is (as I understand it) not compatible with publishing sites, there are a couple of reasons for this.

There is one control called PageRenderMode that can be used on a master page, web part page or page layout. This control has one property called RenderModeType which can have one of two possible values; Standard or MinimalDownload. If the control is placed on a page and have the property set to Standard – it will prohibit the page from being rendered using MDS. If the control is not present or if it’s property is set to MinimalDownload it can participate in MDS rendering. So this control can be used on specific (master)pages to prohibit MDS.<SharePoint:PageRenderMode runat="server" RenderModeType="MinimalDownload" /> 

PageRenderMode control set to MinimalDownload whenever the publishing features are enabled and you have the ribbon on the page, specifically when using the PublishingRibbon in your master page, SharePoint will automagically inject, during runtime, the PageRenderMode control with the property set to Standard.

The MdsCompliant attribute is set on the whole Microsoft.SharePoint.dll assembly, but not on the Microsoft.SharePoint.Publishing.dll assembly. This is a bummer. This means that all the Field Controls, used in page layouts, are not MDS compliant – which means no MDS on publishing sites

Distributed Cache service : The Distributed Cache service gives caching highlights for SharePoint Server 2013. The Distributed Cache service is actually based on Windows Server AppFabric (Windows Server Caching Mechanism), which manage the AppFabric Caching service.Addionally, Windows Server AppFabric installs with prerequisites for SharePoint Server 2013.

The Distributed Cache service  improves performance of the following features in SharePoint 2013:

• Authentication
• Newsfeeds
• OneNote client access
• Security Trimming
• Page load performance

Any server in the farm implemented with the Distributed Cache service is called as a cache host and cache cluster is the group of all cache hosts in a SharePoint Server 2013 farm. A cache host joins a cache cluster when a new application server running the Distributed Cache service is added to the farm.

When using a cache cluster, the Distributed Cache spans all application servers and creates one cache in the server farm. The total cache size is the sum of the memory allocated to the Distributed Cache service on each of the cache hosts.