Use previewing documents is a matter of retrieving a small graphical pre-generated image. This is done at high speed with a very little workload.
The file previews are pre-generated and cached by the Ontolica Conversion servers.
Ontolica Preview does not rely on OWA servers and do not need resources for generating previews as people access documents.
During the initial implementation of Ontolica Preview, all file previews are not available until the initial conversion process has completed.
However, you can configure document libraries less frequently accessed to use the on-demand conversion process which is similar in architecture as the OWA except it supports +500 file formats and is significantly faster.