Does anti-virus software have an impact on MIKE product performance?

Anti-virus software having a negative impact on performance is a well-known fact. It can have a negative impact on both the general performance of a computer/image and a specific application.

The performance impact of the anti-virus software depends on various factors:

1. The application itself

2. How the anti-virus software is configured

3. How the applications are utilized

There are many different anti-virus products on the market. Unfortunately, we cannot test them all, and the degree of negative impact may differ between products and their local configuration.
The negative performance impact of anti-virus software is a 'penalty' for a high IT-security level. The risk assessment and IT-security level is up to the client and something we do not interfere with, and we cannot guarantee the application will not be infected after installation and use in the client’s environment. 

As a product vendor, we are aware of the potential negative effect of anti-virus software on our software and especially a potential reduction in performance for MIKE FM simulations. It is our experience that the negative impact is primarily due to the anti-virus software scanning output files, which are created and modified during a simulation. If so, the performance can be improved by excluding output files from scanning by configuring the anti-virus software accordingly. The most important candidates for exclusion would be files with extension dfs0, dfs1, dfs2, dfs3 and dfsu, when running MIKE FM simulations. Other file types may be relevant for other applications. Another approach is to exclude a specific disk location from scanning (for example, the simulation work directories of the simulations). However, please note that we do not make any specific recommendations due to the reasons mentioned above.

There are also a few more ways to attempt to reduce the impact on performance. As output files are scanned when modified, the output frequency may be evaluated and limited to only the necessary output. In these cases, large output files and timeseries files (dfs0 files) are good candidates to look at since these often have a high output frequency. When running MIKE FM simulations in parallel mode, quite often the number of subdomains or threads are set to the total number of cores available on the system. In this case, there will be a MIKE FM process running on each core and all cores are at maximum load. If an anti-virus scan starts (thereby requiring CPU resources), at least one of the cores will have to be shared between MIKE FM and the scanning. Consequently, the MIKE FM process running on this core will be slowed down, as will the whole MIKE FM simulation since the MIKE FM processes running on the other cores will have to wait for the slower process to catch up. The impact on performance from this may be significant, but can be limited by not using all available cores for the MIKE FM simulation (for example, the number of available cores minus one). This may also be relevant in other cases, depending on the job mix on the system in question. 


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