ABSTACT
1.NAND flash memory (主要缺点):
(1)partial page updates
(2)general-purpose cache usually does not specifically consider and eliminate duplicated contents, despite its popularity.
2.way
Content Cache :logs the latest contents in a high-speed temporary storage
Instroduction
1.FTL2 : a hybrid Flash Translation Layer with Logging
The basic idea: log recently updated contents in a high-speed temporary storage called Content Cache before data reach flash memory
2. FTL2 identifies partial page updates by comparing the differences between the current and new page contents. New data which are part of a page are stored (“logged”) in Content Cache. They are applied back to the original page for read requests on-the-fly.Therefore, time-consuming flash page writes are transformed into fast flash read and DRAM read/write operations.
FTL2
1.The number of updated bytes is obtained by the Update Analyzer. If it exceeds a predefined threshold,the request will be handled by the mapping mechanism. Otherwise,new contents are stored in Content Cache, avoiding one page write operation in flash memory.
更新的字节数是由更新分析仪获得。如果超过一个预定义的阈值，该请求将被处理的映射机制。否则，新的内容存储在内容的缓存，避免一页写操作在快闪记忆体。
2. 在3.2有offset（position of the segment）、bytes （update length）和 a page log 定义（update length）
3.Update Analyzer use XOR
4.对于update 还有 logging threshold (e.g.5%)
5.Content Cache 里面包涵 LRU算法（3.3 结尾）