Calculate Required Archive Size

Historian will asynchronously create a new empty archive when data starts loading into an existing archive. Whenever the current archive becomes full, Historian will immediately serve data to a newly created archive. This significantly reduces archive creation and transition time. If the option to automatically create archives is not enabled, however, you must open a new archive manually. As of Historian 7.0, Historian archives are time-based only.
CAUTION: When the default size limit is reached, if automatic archive creation is disabled and you do not manually create a new archive, new data will not be written to the archives .
CAUTION: If the available disk space is less than the configured amount of free disk space, Historian cannot automatically create new archives.
If you enable the Overwrite Old Archives option, the system replaces the oldest archived data with new data. Since this action deletes historical data, exercise caution in using this feature. Be sure that you have a backup of the archive so that you can restore it later.

If you enable the Overwrite Old Archives option and if you want to retrieve time-based information, create an additional archive to overcome the early loss of data due to archive preparedness. For example, if you want to save 12 months of data into 12 archives, create 13 archives.

During archiver startup and every 60 seconds while the server is running, Historian checks to make sure that you have configured enough free disk space to save the archives, buffer files, and log files. If there is insufficient disk space, the Data Archiver shuts down and a message is logged into the log file. For each archive, you need approximately 1MB of archive space for every 1000 tags, for tag information.

By default, you can view the Historian archiver log file in Historian Data\LogFiles
[03/03/10 15:28:41.398] Insufficient space available in [d:\Historian\Archives\] 
[03/03/10 15:28:41.399] The server requires a minimum of [5000 MB] to continue 
[03/03/10 15:28:41.679] USER: DataArchiver TOPIC: ServiceControl MSG: DataArchiver(DataArchiver) Archiver s 
[03/03/10 15:28:41.807] DataArchiver Service Stopped. 
[03/03/10 15:28:41.809] [d:\Historian\LogFiles\DataArchiver-34.log] Closed.
Archive size is a function of the rate at which you archive data and the time period that you want the archive to cover. You may want the archive to cover a time period of perhaps, 30 days.
Factors that affect the rate at which you archive data are:
  • Number of tags a large number of tags increases the data rate.
  • Polling frequency of each tag a high polling frequency increases the data rate.
  • Compression settings disabling compression or setting narrow deadband parameters increases the data rate.
  • Data types choosing data types that increase the number of bytes per value increases the data rate.
The following is an example of a manual calculation of required archive size, using typical parameter values.
Table 1. Assumptions
Number of tags5000
Polling rate1 value/5 seconds
% Pass Compression5% (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.
If you believe the calculated 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://support.ge-ip.com/devsupport/ to download this and other GE Intelligent Platforms freeware product solutions.