When there are several web applications running under different application pool accounts to ensure security separation you will experience this issue when blob caching is enabled for more than one of the web applications but proper rights are not manually added on the file system path for the blobcache folder. This can cause web applications to become slow or inaccessible.
You will see errors like the following accruing in the event logs:
A runtime exception was detected. Details follow.
Message: Access to the path 'DRIVE:\blobCache\#########2\' is denied.
System.UnauthorizedAccessException: Access to the path 'DRIVE:\blobCache\#########2\' is denied.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.Directory.InternalCreateDirectory(String fullPath, String path, DirectorySecurity dirSecurity)
at System.IO.Directory.CreateDirectory(String path, DirectorySecurity directorySecurity)
at Microsoft.SharePoint.Publishing.BlobCache.CreateDirectory(String directoryName)
at Microsoft.SharePoint.Publishing.BlobCache.WriteIndex(Boolean tokensOnly)
at Microsoft.Office.Server.Diagnostics.FirstChanceHandler.ExceptionFilter(Boolean fRethrowException, TryBlock tryBlock, FilterBlock filter, CatchBlock catchBlock, FinallyBlock finallyBlock)
An error occured in the blob cache. The exception message was 'Access to the path 'DRIVE:\blobCache\#########2\' is denied.'.
Workarounds in order of easiness:
1. Use a different root blobcache folder for each application.
To work around this issue you can specify a different folder when configuring blob caching for each web application in the web.config.
<BlobCache location="DRIVE:\blobCache" path="\.(gif|jpg|png|css|js)$" maxSize="10" max-age="86400" enabled="True"/>
If you set the BlobCache locations to the following you should avoid this problem:
Web Application Location
2. Manually give <LOCALMACHINE>\WSS_WPG full control to DRIVE:\BlobCache.
3. Use the same app pool account for any applications you plan to enable blobcaching on.
Article ID: 2015895 - Last Review: 03/05/2010 15:59:00 - Revision: 3.0