Configure BLOB cache settings in SharePoint 2010

Blob cache is a quick and easy way to speed up your SharePoint site.

Here’s the MS blurb

A BLOB cache is a disk-based cache that stores binary large objects (BLOBs) such as frequently used image, audio, and video files, and other files that are used to display Web pages. Each front-end Web server maintains its own BLOB cache. When you enable a BLOB cache, you specify the file types to include in the cache and also the location of the BLOB cache. The first time that a BLOB file is requested, the file is copied from the database to the BLOB cache on the front-end Web server. Future requests to the front-end Web server for that same file are then served from the file that is stored in the BLOB cache, instead of being served from the database. This reduces the network traffic and the load on the database server.

To Enable Blob Cache

1. Make a copy of your web.config, open the live web.config

2.   Find the line <BlobCache location="" path="\.(gif|jpg|jpeg|jpe|jfif|bmp|dib|tif|tiff|ico|png|wdp|hdp|css|js|asf|avi|flv|m4v|mov|mp3|mp4|mpeg|mpg|rm|rmvb|wma|wmv)$" maxSize="10" enabled="false" />

3.  Change the location to a location that exists on each of your WFE’s. (Each WFE will have a cache dir, doesn’t have to be a share)

4.  Amend which files you want to cache by removing those you don’t want to cache.

5. Change the maxsize variable to something your drive location can cater for, size is in GB. (Note each IIS website will use this value, 3 sites = 30GB if set to 10)

6. Change the enabled attribute to “true” from “false”

7. Save the web.config file and load your site.

8. Check the blob cache gets created on each WFE.

To Flush the BLOB cache (SharePoint Server 2010)

When you flush the BLOB cache, you clear the contents of the BLOB cache for a Web application. This is useful if the BLOB cache becomes out of sync with the content. For example, after you restore a content database, the BLOB cache will be out of sync with the content. To correct that situation, you must flush the BLOB cache.

Create a PS script file containing the following.

$webApp = Get-SPWebApplication "<MyWebApplicationURL>"

[Microsoft.SharePoint.Publishing.PublishingCache]::FlushBlobCache($webApp)

Write-Host "Flushed the BLOB cache for:" $webApp

Save the file “FlushMyWebApplicationURL”, and test run it to see that the Blob Cache gets deleted.

Test show this  updates the files in the blobcache dir but doesn’t remove all the files entirely.

 More info on the MS site here : 

http://technet.microsoft.com/en-us/library/cc770229.aspx#BLOB