English to Chinese Tech/Engineering IT (Information Technology) 缓存

A block that hasn’t been read or overwritten between two scanner passes is demoted to a “cooler” status

Multiple scanner passes occur before a block is evicted from cache

Blocks inserted using the read cache policy that are read before the next scanner pass are promoted to a warmer status
请教这三句话里面的scanner pass是什么意思，这里讲的是缓存的处理机制。谢谢！