Relocating the cache file
When you configure a drive for caching, Microsoft Forefront Threat Management Gateway creates a cache content file (Dir1.cdat) in the drive:\urlcache folder. This default location can be changed.
You can specify an alternative cache file location on the drive, including an environment variable such as %cacheDirectory%. If the specified folder does not exist, Forefront TMG will warn you that the specified location is not valid and will try to create the folder.
For any alternative cache folder, the Network Service account must have read permissions from the root partition and any parent folder for the folder. For the cache folder, the following permissions are required:
Network Service: Full Control
System: Full Control
Administrators: Full Control
If you do not set permissions correctly, the following error event may be issued: 14176: "Disk cache drive:\urlcache\Dir1 failed to initialize. Identify the reason for cache failure by examining previous recorded events, or the error code. Check that the disk is connected and that it is not corrupt."