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FortiGate unit running very slowly

You may experience a number of problems resulting from your FortiGate unit being overloaded. These problems may appear as:

  • CPU and memory threshold limits exceeded on a continual basis
  • AV failopen happening on a regular basis
  • dropped traffic or sessions due to lack of resources

These problems are caused by a lack of system resources. There are a number of possible reasons for this.

Too many VDOMs

If you have configured many VDOMs on your system, past the default ten VDOMs, this could easily be your problem.

Each VDOM you create on your FortiGate unit requires system resources to function - CPU cycles, memory, and disk space. When there are too many VDOMs configured there are not enough resources for operation. This may be a lack of memory in the session table, or no CPU cycles for processing incoming IPS traffic, or even a full disk drive.

Go to Global > System > VDOM and see the number of configured VDOMs on your system. If you are running 500 or more VDOMs, you must have a FortiGate 5000 chassis. Otherwise you need to reduce the number of VDOMs on your system to fix the problem. Even if you have the proper hardware, you may encounter noticeably slow throughput if you are using advanced features such as security profiles or deep content inspection with many configured VDOMs.

One or more VDOMs are consuming all the resources

If you have sufficient hardware to support the number of VDOMs you are running, check the global resources on your FortiGate unit. At a glance it will tell you if you are running out of a particular resource such as sessions, or users. If this is the case, you can then check your VDOMs to see if one particular VDOM is using more than its share of resources. If that is the case you can change the resource settings to allow that VDOM (or those VDOMs) fewer resources and in turn allow the other VDOMs access to those resources.

Too many Security Features in use

It is likely that reducing the Security Features in use regardless of number of VDOMs will greatly improve overall system performance and should be considered as an option.

Finally it is possible that your FortiGate unit configuration is incorrect in some other area, which is using up all your resources. For example, forgetting that you are running a network sniffer on an interface will create significant amounts of traffic that may prevent normal operation.