Technical Alerts

Peformance issues with SmartFilter content filter and ProxySG

Technical Alerts ID:    TFA26
Version:    5.0
Status:    Published
Published date:    03/02/2010
Updated:    03/02/2010
 

Problem description

There is a potential performance issue that may arise with ProxySG units that are utilizing SmartFilter onbox content filtering and the "Normal" memory allocation given to the content filter database by SGOS.  Some of the symptoms include:

  • High CPU utilization
  • Slow performance
  • An ever increasing number of client workers, or the client workers being maxed out

 

The problem is the size of the content filtering database and the amount of RAM that is allocated to keeping the SmartFilter database in memory.  Over time, the size of the content filter database has increased.  Recently, as of the writing of this article, the SmartFilter database grew beyond 350MB in size.  Older versions of SGOS do not have the ability to allocate more memory to the content filtering database.  As the size of content filter databases grow, the end result is the content filter database cannot all reside in RAM and the ProxySG has to page the content filter database in and out of RAM.  If the ProxySG is busy, this paging can cause the proxy's performance to dramatically decrease.  Starting with SGOS 4.2.7.1 and SGOS 5.2.3.2, SGOS can be configured to allocate a "High" amount of memory to a content filter database.  Please refer to the table below to see how much memory is allocated per memory setting:

Total ProxySG RAM Low Normal High
512 MB 1MB 50MB 50MB
1GB 1MB 120 - 200 MB 120-200MB
Depends on the platform
1.5GB 1MB 200MB 350MB
2GB 1MB 250MB 600MB
3GB 1MB 250MB 1.1GB
4GB 1MB 350MB 1.6GB

 

On some of the low-end proxies, even setting the memory allocation to "High" may not be enough to eliminate or minimize the amount of paging that may occur.  It may be necessary to upgrade the hardware to a model that has at least two GB of RAM in the device in addition to setting the memory allocation to "High".  SGOS 5.4.3.x allows better paging of the database to disk, but if paging does occur, there is still a possibility of peformance degradation occurring.

NOTE:  Even though the ability to set the amount of RAM allocated to the content filter database has been in since SGOS 4.2.7.1 and 5.2.3.2, Blue Coat recommends that customers upgrade to the latest version of SGOS to address other issues that may affect performance and stability.  For those customers that are running SGOS 4.x code and are experiencing this issue, please contact Blue Coat or your reseller about obtaining the patch release version 4.3.3.9.

For further information about this issue, please see KB3709.


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