OS: 250 GB NVME SSD
SSD: 300GB data/ 200 GB primocache L2
HDD: 1500 GB games (cached) / 1500 GB data
Now I noticed that when installing games I run into the HDD speed cap instead of my internet speed (400 Mbit). I enabled defer writing BUT there was absolutely no write activity on the SSD. What I expected to happen was that the game would be downloaded to the caching SSD and then in the background the data would be synced to my HDD. I even tried 'buffer' mode with 60 seconds defer but it did not happen. It is only using the 500MB RAM for deferring.

Read caching is working as expected (used data get's moved to the SSD).