Calculate Disk Storage

Equations allow you to calculate the total disk space necessary to store a trend across a specified period of time.

The storage method used for a trend (Scaled or Floating Point) affects the number of bytes necessary for each sample, so in order to calculate the disk space necessary correctly it is important to base your calculations on the appropriate formula. By default, the Scaled storage method is used.

Floating point

Each data sample requires eight bytes of storage. This alters the equation to:

The number of bytes necessary then becomes:

Scaled

Each data sample requires two bytes of storage. You can therefore calculate the total disk storage necessary for each trend by using the following formula:

For example, if a trend record produces one sample every ten seconds for one week, and you are using five data files (five weeks), the number of bytes necessary is:

Note: The calculations above do not take into account the space necessary to store the history file for each trend. This is because these files remain at a set size and therefore do not significantly impact the amount of disk space necessary.

Note: For efficient trends storage, use Windows file compression. By using this method you often can reduce your files to 10% of their original size; the actual amount of compression varies depending on the rate of change of the data.

See Also

Reconfigure History Files