In general, the total cache size should be x1.25 bigger than the total size of the data that need to be cached - cache eviction kicks in when the SSD usage reaches 80%.
You can calculate the required cache size with the following formula:
(Total cache needed)/0.8 - (total size of the data that need to be cached)/0.8 = Total cache size
Aggregating indexes are also stored in cache.
As a rule of thumb, we always recommend using more SSD than needed to leave enough space for future data that will be loaded.
When turning on the engine, you will be able to see the amount of data that is pre-warmed, thus making adjustments to the size of the engine (at the beginning, metadata and system parts being preloaded as well)