You touched on multiple aspects. Here are some thoughts and observations from my tests:
- A) Yes … the cache file should extend to max cache size right after adjusting it in the settings
- B) … but some people report that they cannot adjust the size at all.
- C) Yes … from the outside you cannot tell how much actual data is in the cache
- D) I so far have not seen any hint how the cache is actually operated, meaning …
- how and when space in this buffer is reused (FIFO, LRU, TLRU, … etc),
- how the index is handled (is there some embedded SQLite index?)
- E) Fragmentation would be an issue on HDDs … but has no impact of SSDs
- … the zero prefill (today, in the SSD age) seems to be more about pre-claiming the large space on the disk, so that no other process will grab it “behind” the sims back.
- F) Most of the sound (now) seems to come from files on disk … not the rolling cache.
- G) I fear (hope?) that the stutters are not related to the cache.
- In contrast to FS2020 I am now no longer “main thread limited” … and so I do hope that all the cache and network handling is no longer affecting the main thread.
I am using an AMD card and in FS2024 so far flights have been really smooth. But there are other reports on this thread too … and so obviously something is still “not smooth” with the data pipeline … from the servers to the VRAM.
If you are interested in my RollingCache recordings (where I for example stumbled over the sound data source) you can look here:
It might provide you with some helpful “order of magnitude” data volumes to allow a good guess about how much data gets written to the cache over a certain period of time (say a flight at 3,600 ft at 180 ktas).