in which scenario to use object cache for a intranet web application that is accessible by internal users in a domain, this intranet is publishing site. and differences between object cache and blob cache?
Object cache -
Object cache 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 hit. Features of SharePoint that uses Object cache are publishing, content query web part, navigation, search query box and metadata navigation. There are only a few things you can do about this type of cache - set size.
BLOB cache -
If your Site is publishing Site, then you should use the Publishing Cache as "The goals of the object cache are to reduce the load on the computer on which SQL Server is running, and to improve request latency and throughput". Key here is you should properly configured the Object Cache with Portal Super User and Portal Super Reader account. If you trying to use the default settings(without Proper Account) then your will see tons of errors in the ULS logs and Event Log related to the Object Cache.
For Blob Cache: Again, this is reduce the traffic between the SQL server and SharePoint servers.As Blob Cache Control the caching of Binary objects,such as frequently used image, audio, and video files, and other files that are used to display web pages, such as .css and .js files. Once it store on WFE, then Web server get the data from there rather making a trip to the SQL server.
Base your decision to enable BLOB caching on the following criteria:
- For a publishing site for which most of the visitors are anonymous or where most of the files are static content, enable the BLOB cache for as many file types as possible.
- For a publishing site that plans to use the image renditions feature, you must enable the BLOB cache.
- For other sites that contain lots of media assets that are read-only, or where only a small percentage of the media assets are updated, enable the BLOB cache for media files only.