Setting Archive Size

Since archived data files can become quite large, you should adjust system parameters carefully to limit data collection to meaningful data only and minimize the required size of system storage. This chapter describes techniques you can use in your application to accomplish these goals. Historian now supports a maximum Archive Size of 256 GB per archive.

Note: When you start Historian, it may take a longer time to start an archiver depending on the number of archives online, number of tags, and number of connections.

For each archive, you need approximately 1MB of archive space for every 1000 tags to store tag information. Archive size is a function of the rate at which you archive data and the time period you want the archive to cover. A typical user wants the archive to cover a time period of, say, 30 days. Factors that affect the rate at which you archive data are

Factors that affect the rate at which you archive data are:

  • Number of tags: A large number of tags.

  • Polling frequency of each tag: A high polling frequency of each tag.
  • Compression settings: Disabling compression or setting narrow deadband parameters.
  • Data types: Choosing data types that increase the number of bytes per value.

Example

The following is an example of a manual calculation of required archive size, using typical parameter values. This example archive needs to contain data collected over 30 days.

Assumptions:
  • No. of tags: 5000
  • Polling rate: 1 value/5 seconds
  • % Pass Compression: 5%. Pass Compression is the number of data values archived relative to the number of values read, expressed as percent.
  • Bytes/value: 4
  • Duration: 1 month (30 days)
Calculation:



The calculation shows that a file size of 500 MB is adequate for archiving one month of data for this application.

It is recommended that you set the default archive size to 500 MB for systems with 1000 tags or more. If you believe the computed size is too large for your application, you can modify parameters as follows:
  • Decrease the polling frequency.
  • Increase compression deadband, reducing the pass percentage.
  • Reduce the number of tags.
  • Add more disk capacity to your computer.

Archive Size Calculator

An Archive Size Calculator tool is available to estimate archive size based on your input and estimates the archive size and collector compression based upon a tag that has already been configured. Log on to http://digitalsupport.ge.com to download this and other GE Intelligent Platforms freeware product solutions.