Looking at services like Amazon Redshift, which is meant for storing petabytes of data. What forms of data are meant to be stored here? Logs, raw data?
The question for a data warehouse is not what kind of information you store in it but rather how you store it and what you inted to use it for. Any data an organisation needs to analyze and compare may be put into the data warehouse.
To define a data warehouse is very difficult and you'll probably get as many definitions as people you ask. I've seen lots of different implementations and no one can really say that this is a data warehouse and this is not. However there are a number of key points that a data warehouse normally should fulfill, namely that it should be time variant (i.e. store datapoints over time) and it should be non-volatile (i.e. you never update data in a data warehouse, you only insert).
Following these rules allow you to the most common data warehouse analysis, namely analyze data over time, e.g. compare this seasons sales with last season.I'm not sure what Amazon Redshift actually do, but if it is a data warehouse or not I think is more a question of how you use it.