Forefront Security for SharePoint Best Practices - Bias setting
Applies to: Forefront Security for SharePoint
Topic Last Modified: 2007-12-07
The bias setting controls how many engines are used to provide you with an acceptable probability that your system is protected (realizing that there is a trade-off between virtual certainty and system performance). The more engines you use, the greater the probability that all viruses will be caught. However, the more engines you use, the greater the impact on your system’s performance. While Forefront Security for SharePoint uses a very efficient in-memory scanning process, each additional engine adds to scanning time and resource usage.
Thus, at one extreme is the number of engines to use for maximum certainty. The other extreme is the number of engines that will allow maximum performance. It is recommended that, in general, you use all available scan engines.
You can have a different bias setting on different servers, depending on your needs. For example, you might want to use only a single engine on your gateway server, to maximize its performance. Then, you can use several engines on your other servers where performance is not as critical.
When using Maximum Certainty, scanning is held up any time a scan engine is being updated because Maximum Certainty requires that every file be scanned by every selected engine. To provide complete scan engine coverage, scanning is queued until the scan engine update is finished (typically less than 30 seconds). To avoid this, you can select Favor Certainty, with which scanning will continue, with all available engines, while an engine is being updated.
It is recommended that you start with Favor Certainty, since the safety of the infrastructure should be your main concern. This setting will ensure that all the available engines are utilized (those that are not being updated) and that no files can be opened without having passed through the maximum number of engine scans.
It is recommended that the settings be the same as those you select for the Realtime Scan Job.