Content Cache: Settings and Statistics

HTTP > Configuration > Content Cache | Settings and Statistics

Web content caching is the caching of Web objects (e.g., HTML pages, images) to reduce bandwidth usage, server load, and perceived lag. A Web cache stores copies of objects passing through it. Subsequent duplicate requests may be satisfied from the cache if certain conditions are met. Cached objects will be re-scanned by IWSVA

The Content Cache capability provides users who access the Web through IWSVA with a quicker experience while saving bandwidth.

Note: This feature is available only in Forward Proxy mode. If the deployment mode changes from Forward Proxy mode to another mode, the Content Cache features is greyed out and will not function.

With the Content Cache feature, administrators enable or disable the IWSVA in-box cache and manage caching through Web console. It also generates cache statistics.

Note: The Content Cache feature cannot be disabled from the CLI.

Enabling/Disabling the Content Cache

To enable/disable the Content Cache feature:

Check the Enable Content Cache check box at the top of the page to enable the Content Cache feature.
Click Save.
Uncheck the Enable Content Cache check box to disable the Content Cache feature.
Click Save.

Clearing the Content Cache

In order to clear the cache, first disable the Content Cache feature.

To clear the Content Cache:

Disable the content cache.

The Clear Cache button is disabled when the Content Cache feature is enabled.

Click Clear Cache. You receive the following warning:

"It could take a significant amount of time to clear a large cache.

Are you sure you want to clear the cache?"

Click OK. A progress bar displays during the cache clearing process.

The Clear Cache button and the Enable Content Cache check box are both disabled until the clearing process ends. After the cache clears, the "Last purged date" updates.

Managing the Content Cache

Administrators can configure the following content cache areas:

Hard disk usage for the Content Cache
Cache object size

To manage the Content Cache:

Go to the Hard Disk Usage for Content Cache section of the Content Cache Settings and Statistics tab.

Enter a quantity for the Cache space size.

Administrators can adjust the amount of disk space used to store the cached content. A larger cache volume will allow more web objects to be cached. A smaller cache partition will reduce the number of cacheable objects. If you set the cache volume too small and run out of disk space for caching, the hit ratio may decrease as IWSVA will rely more on real-time content retrieval and less on locally cached content.

Perhaps your VA total partition space is 40GB within binaries, files and log occupying 15GB. Currently, your "Assigned cache space" setting might be 10GB, and the "Cache space in use" might be 5GB. The screen would show:

Available cache space: 25,000MB [40GB (total space) - 15GB (logs, etc)]
Assigned cache space: 10,000MB
Cache space in use: 5,000MB

In this case, the "Assigned cache space" setting could be increased to a maximum of 25GB.

To tune the minimum and maximum size values, select the amount and unit of measure (KB/MB) for the following:

Minimum size of object to be cached (default 0KB) Range allowed is: 0-10240KB/10MB
Maximum size of object to be cached (default 10MB) Range allowed is: 1-4096MB/4194304KB

You can experiment with the minimum and maximum size values to fine tune the cache performance and hit rate for your environment. Trend Micro recommends starting with the default values and then fine tuning as necessary for your environment. MORE>>

The minimum size and maximum size of cached objects will allow you to tune the caching performance. If the minimum size of cached objects is set too small, the cache service will use local resources to cache content that can be retrieved more quickly from the Internet and this can slow performance. If the minimum size is set too large, the cache may not contain popular objects that can save bandwidth and reduce latency.

This is also true for the maximum size of cacheable objects. Depending on the type of web pages users access, and what type of cacheable objects they contain, the performance will vary.

Click Save.

Real-time Statistics

The real-time statistics for the Content Cache feature include:

Cache Statistics	Description
Request hit ratio	The percentage of HTTP requests that result in a cache hit.
Byte hit ratio	Compares the number of bytes received from origin servers to the number of bytes sent to clients. When received bytes are less than sent bytes, the byte hit ratio is positive. However, a negative byte hit ratio might occur if clients abort multiple requests before receiving the entire response.
Cache disk usage	The amount of data currently cached on disk.
Number of objects in cache	Represents the number of objects cached.

Note: Real-time statistics for the Content Cache feature will not refresh automatically. You must click the Refresh link for the statistics to update.