Difference Between Object Cache and Output Cache in SharePoint Server

Planning caching in SharePoint is an important matter which have direct impact on the performance of the SharePoint sites. SharePoint Server provides a disk-based binary large object (BLOB) cache that reduces database load and increases browser performance for users. This post describes the difference between object cache and output cache along with a quick overview on BLOB caching in SharePoint.

The Page Output Cache in SharePoint

The page output cache is an in-memory cache that saves rendered ASPX pages. Using Output cache improves performance in two ways first it reduces the amount of SQL calls. Second it reduces workload on the WFE because pages do not need to be re-rendered. Along those lines if the pages are anonymous, then no SQL check needs to be done at all present the cached pages. Microsoft testing concluded a ninefold improvement in throughput when compared to having to render the page every time it was rendered.

The Object Cache in SharePoint

Object cache is a caching option available Microsoft SharePoint Server. What Object cache does is stores metadata about SharePoint Server objects (like SPWeb, SPSite, SPList, etc.) on the WFEs. When a page is rendered, if there is data that needs to be retrieved through these objects, the SQL Server will not be queried, the data will be returned from the cache instead. Features of SharePoint that uses Object cache are publishing, content query web part, navigation, search query box and metadata navigation. These features are specifically written to use the Object cache API instead of the SharePoint API directly.

The BLOB Cache in SharePoint

SharePoint Server provides a disk-based cache that stores files that are used by Web pages to help them load quickly in the browser, and reduces the load on the database server when it uses those files. The BLOB cache is stored directly on the hard disk drive of a front-end Web server computer. By default, the BLOB cache is off and must be enabled to use the functionality it provides. When you enable the BLOB cache on your front-end Web server, you reduce the load on the SharePoint Server 2010 database server created by read requests from Web browsers. You enable the BLOB cache in the Web.config file of the Web application to which you want to apply it. The changes that you make to the Web.config file will be applied to all site collections within the Web application.