Remedy's Alan Wake features just 2.41GB of actual game data for all six of its in-game episodes.
Examination of the XDVDFS partition of the shipping retail disc shows that an additional 3.74GB is allocated on top of that for the range of full-motion video sequences that pepper the game - a fact made all the more remarkable owing to the inclusion of audio support for a mammoth seven different languages. The combined total brings Alan Wake to 6.15GB for the final shipping product.
Bearing in mind that the game takes between 10 and 16 hours to complete, 2.41GB of data is a remarkable achievement. Playing through the survival-horror psychological shooter, only the appearance of the occasional low-resolution environment texture gives any kind of clue of the levels of compression that Remedy has achieved.
So, how did they do that? Probably the most crucial factor to point out is that Alan Wake is set in a single locale: Bright Falls. Looking at the way the disc is structured, episode one seems to get over half of the data allocation while the additional episodes appear to be "bolt-ons" that are much, much smaller.
Factoring that in, along with the fact that Alan Wake originally began life as an open-world style of game (typically highly compressed for fast on-the-fly data streaming), the structure makes perfect sense. Since we are dealing with a single location, Remedy is able to re-use a lot of rock, dirt, road and other environmental artwork across all the six episodes.
Assuming Wake remains in Bright Falls, it also means that any future DLC can tap into these existing assets too: chances are that the additional video sequences will occupy the lion's share of the download.
In terms of those video sequences, the majority of that 3.74GB is dedicated to over 60 cinematic sequences that account for around 80 minutes of playback. However, interestingly, Remedy has utilised video in some fairly innovative ways. For example, all of the TVs dotted around the Bright Falls game world are running small 96x96 videos. Some menu backgrounds are also looping video, while Alan's occasional split-second "flashes" are also streamed in from that same video directory.