eG Monitoring
 

Measures reported by FTMGCacheTest

Forefront Threat Management Gateway (TMG), when deployed as a web proxy server, can be configured to cache frequently requested web objects in memory and on disk in order to improve web browsing performance and to reduce bandwidth utilization. Web content caching is available for both forward and reverse proxy scenarios. Content caching brings with it different benefits in each of these deployment scenarios.

With content caching enabled, when the TMG firewall receives a web proxy request the firewall will first attempt to fulfill the request from the cache. If the requested content does not exist in the cache, it will make the request of the origin server as normal. When the web server responds, TMG will return the content to the client, and then store any cacheable content in the cache. Subsequent requests for the same content will be served directly from the cache and returned to the client at LAN speeds, eliminating the need to make a trip to the origin server to retrieve the content. This improves page loading speeds for end users and reduces bandwidth consumption on Internet links.

This test monitors the caching capability of the Forefront TMG and reports the following:

  • The rate at which the data is retrieved from the disk and memory that is allocated for content caching
  • The rate of I/O operations that failed
  • The rate at which URLs are stored and retrieved from the disk and the memory
  • The ratio of memory cache to the overall cache
This way administrators can be proactively alerted on the caching capability of the Forefront TMG and should there be any discrepancy, the administrators can fine tune the caching capability which eventually would result in higher web browsing performance and resuced bandwidth consumpton on internet links!

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
DataFromDC Indicates the rate at which data is retrieved from the disk drive that is allocated for content caching in this firewall. KB/Sec A high value is desired for this measure.
DataFromMc Indicates the rate at which data is retrieved from the memory that is allocated for content caching in this firewall. KB/Sec  
DiskFail Indicates the rate at which I/O operations failed on the disk that is enabled for content caching since the start of the firewall service. Number An I/O failure occurs when the Forefront TMG fails to read from or write to the disk. A low value is desired for this measure. A steady increase in this value indicates that the requested web objects are not available in the cache and the Forefront TMG services the requests from the cilent - this way the web browsing performance is highly affected along with a steep increase in the bandwidth utilization.
DiskWrite Indicates the rate at which data is written to the disk that is allocated for content caching. KB/sec A high value is desired for this measure.
TotalDiskFail Indicates the number of times the Forefront TMG failed to read from/write to the disk since the start of the firewall service. Number A low value is desired for this measure. A steady increase in the value of this measure is a clear indication of the inability of the cache to cater to the requests which would eventually lead the Forefront TMG to look to the clients for the requested web object thus increasing the bandwidh utilization and reducing the web browsing performance.
UrlCommit Indicates the rate at which the URLs are stored in the disk that is allocated for content caching. Urls/sec  
DiskUrlRetrv Indicates the rate at which the URLs were retrieved from the disk. Urls/sec A high value is desired for this measure.
MemUrlRetrv Indicates the rate at which the URLs were retrieved from the memory. Urls/sec  
DiskCacheSpace Indicates the amount of space that is allocated for content caching in the disk. KB  
MemCacheSpace Indicates the amount of space that is allocated for content caching in the memory. KB  
MemUsage Indicates the ratio of fetches from the memory to the total fetches from the overall cache, expressed as percent. Percent This measure is a good indicator to identify how well the memory has been utilized for content caching.
CacheUrl Indicates the number of URLs that are currently stored in the cache. Number A high value is desired for this measure.