vSAN cache recommendations for vSAN 5.5 were 10% of used capacity. With the addition of all all flash in 6.0 it stayed at 10% and Cormac here explains the math behind this. Now if you look closely you’ll notice a few issues as vSAN and flash drives have progressed. The 10% ratio guidelines was based on a
Quelle: Designing vSAN Disk groups – All Flash Cache Ratio Update – Virtual Blocks