一、寫命中場景
Write-through- Write is done synchronously both to the cache and to the backing store. （維基百科定義）
翻譯：Write-through（直寫模式）在數據更新時，同時寫入緩存Cache和後端存儲。此模式的優點是操作簡單；缺點是因爲數據修改需要同時寫入存儲，數據寫入速度較慢。
試用場景，讀多寫好，相對來說寫時延在整個業務場景下佔比不大。
Write-back (or Write-behind) - Writing is done only to the cache. A modified cache block is written back to the store, just before it is replaced.（維基百科定義）
翻譯：Write-back（回寫模式）在數據更新時只寫入緩存Cache。只在數據被替換出緩存時，被修改的緩存數據纔會被寫到後端存儲。此模式的優點是數據寫入速度快，因爲不需要寫存儲；缺點是一旦更新後的數據未被寫入存儲時出現系統掉電的情況，數據將無法找回。
試用場景，寫多，或者讀寫平均的場景。
二、寫不命中場景
Write allocate (also called fetch on write): data at the missed-write location is loaded to cache, followed by a write-hit operation. In this approach, write misses are similar to read misses.。Write allocate：先把要寫的數據載入到Cache中，寫Cache，然後再通過flush方式寫入到內存中； 寫缺失操作與讀缺失操作類似。
No-write allocate (also called write-no-allocate or write around): data at the missed-write location is not loaded to cache, and is written directly to the backing store. In this approach, only the reads are being cached。No write allocate：並不將寫入位置讀入緩存，直接把要寫的數據寫入到內存中。這種方式下，只有讀操作會被緩存
三、維基百科流程圖
（一） write allocate
（二） no-write allocate