Performance impact of storing unstructured data as a separate not analyzed field

I was wondering if a not-indexed field (just stored) will have any impact on the query time? I mean, for the query that we are not even referring to the retrieval of that field. For example, since when you are parsing a log, there might be a chance that you may not able to parse it correctly, we would like to have the unstructured log attached to the document as a sperate field (e.g. raw_date). This field is only stored and may retrieve occasionally. However, I am not sure if there will be any impact on the query time. I can understand that there will be a very small impact on the indexing time (the time it takes to store the additional field) and there will be an impact to disk size (almost doubling the size on disk), but I suspect if there is any impact to the query time as well. I would appreciate it if you could help me to understand that.

Thanks