Determining the necessary number of FactoryTalk AssetCentre agents

An asset can be scheduled for Backup or Backup and Compare by a FactoryTalk AssetCentre agent based on any range of time (for example, once per day, once per week, or once per month.) Determining the number of necessary agents is dependent upon the speed with which an asset can be serviced and how often that asset is scheduled to be serviced.
An agent is capable of servicing approximately 100 assets every 12 hours. This approximation is based on Rockwell Automation testing of various types of devices, network loads, and program file sizes, and should be used for estimation purposes. Using this estimate, for example, a FactoryTalk AssetCentre containing 200 assets does not necessarily need 2 agents (200/100 = 2) Many systems schedule assets to be serviced on a daily or weekly basis, meaning that one agent could be estimated to service all 200 assets in that 24 hour or greater period.
When applying this estimation, note that each asset type will carry a different average, which is further variable when project sizes and network types are taken into account. For more granular estimation, the following averages have been seen in Rockwell Automation testing, but are still subject to variation depending upon the specific application, I/O configuration, and network bandwidth:
  • PLC-5 (90% capacity with several thousand tags on scan per second)
    • Ethernet – approximately 2 minutes
    • ControlNet – approximately 3 minutes
    • Data Highway Plus - approximately 7 minutes
  • SLC 500 (90% capacity with several thousand tags on scan per second)
    • Ethernet – approximately 4 minutes
    • Data Highway Plus - approximately 5 minutes
  • 70 series drives
    • Ethernet/ControlNet/DeviceNet – approximately 1 minute
  • PanelView Plus (with around 1,000 tags on scan per second)
    • Ethernet – approximately 1 minute per 1 MB of project size
    • ControlNet – approximately 2 minutes per 1 MB of project size
ControlLogix estimations are more difficult due to the wide variety of ways a project can be created. Generally, it is highly advantageous to design a ControlLogix project with proper programming procedures as detailed in the ControlLogix Design Considerations (for example, use arrayed tags instead of scattered tags). The performance differences between arrayed and non-arrayed projects, especially in larger program sizes, ranged from noticeable to extreme.
  • ControlLogix L6x/L73 (arrayed tags)
    • Ethernet – approximately 30 seconds per 1 MB of project size
    • ControlNet – approximately 1 minute per 1 MB of project size
      TIP:
      As project sizes approach 70% or more of total memory capacity, upload times will increase more quickly. These estimates assume proper time for communications, as well as the use of ladder diagram routines. SFCs or Function Blocks may cause different compare time results.
  • ControlLogix L6x (scattered tags)
    • Ethernet – approximately 1 minute per 1 MB of project size
    • ControlNet – approximately 2 minutes per 1 MB of project size
      TIP:
      As a project size increases beyond 5MB or 50% memory capacity, upload times will increase dramatically. These estimates assume proper time for communications, as well as the use of ladder diagram routines. SFCs or Function Blocks may cause different compare time results.
  • ControlLogix L73 (scattered tags)
    • Ethernet – approximately 1 minute per 1 MB of project size
    • ControlNet – approximately 1 minute per 1 MB of project size
      TIP:
      As a project size increases beyond 5MB or 50% memory capacity, upload times will increase dramatically. These estimates assume proper time for communications, as well as the use of ladder diagram routines. SFCs or Function Blocks may cause different compare time results.
Also note that the estimations above are based on Backup and Compare schedules returning with no differences found. Depending on the type of compare, more time could be required to generate the compare report. Each production system will be different based on the differences detected, as well as the variables already mentioned (for example, network bandwidth and file size during upload contribute significantly to the amount of time needed to complete the upload.)
When designing a new system or increasing asset count in an existing one, the approximation of 100 assets per 12 hours should be used to determine how many FactoryTalk AssetCentre agents should initially be added to the system. Performance should then be tested, with the FactoryTalk AssetCentre agent count adjusted based on performance needs.
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