====Synchronised and Scattered Historical Sources====

There are two main ways of recording your history.

In most cases, marking your data source as **sychronised** will result in significantly better read performance and less server load.

===Synchronised===

**Synchronised** recording is when you store the information about all of your values at the same time. This means that when you look at your recorded data, there's a complete snapshot with the same date-stamp.

|Date|Name|Value|
|2012-02-03 09:00:00|Alpha.Pressure|1922|
|2012-02-03 09:00:00|Beta.Pressure|2883|
|2012-02-03 09:00:00|Gamma.Pressure|5558|
|2012-02-03 08:00:00|Alpha.Pressure|1922|
|2012-02-03 08:00:00|Beta.Pressure|3922|
|2012-02-03 08:00:00|Gamma.Pressure|3992|

Above, you'll see that there are a complete set of values recorded at 9:00, even though there was no change in the 'Alpha.Pressure' value. This is a //synchronised// recording.

===Scattered===

Scattered recording either only records the //changes// in your data, or records all of your points at different times and rates.

|Date|Name|Value|
|2012-02-03 09:00:00|Beta.Pressure|2883|
|2012-02-03 08:30:00|Gamma.Pressure|5558|
|2012-02-03 08:15:00|Gamma.Pressure|2247|
|2012-02-03 08:00:00|Alpha.Pressure|1922|
|2012-02-03 08:00:00|Beta.Pressure|3922|
|2012-02-03 08:00:00|Gamma.Pressure|3992|

Above, you'll see that there is only a single record for Alpha pressure, while there are many more for Gamma. 

Note that while scattered recording is significantly more efficient in terms of server //write// load and drive usage, it's much more expensive to //read//. This is why the ARDI [[Recorder addon|Recorder addon]] performs synchronised recording.