Write-Back caching improves write speed and lowers the latency while Write-Through caching improves only the read speed. The cache expiry period is the timeframe data is kept in the cache from the moment of the last access before being flushed to the disk. More information about StarWind cache can be found in this document: https://knowledgebase.starwindsoftware.com/explanation/starwind-virtual-san-l1-and-l2-caches-operational-principles/