f2fs针对SSD介质，根据数据读写的频繁程度，实现了冷热数据的分离。
# 多路日志的原理
# 多路日志的相关数据结构
“`
/*
* For SIT manager
*
* By default, there are 6 active log areas across the whole main area.
* When considering hot and cold data separation to reduce cleaning overhead,
* we split 3 for data logs and 3 for node logs as hot, warm, and cold types,
* respectively.
* In the current design, you should not change the numbers intentionally.
* Instead, as a mount option such as active_logs=x, you can use 2, 4, and 6
* logs individually according to the underlying devices. (default: 6)
* Just in case, on-disk layout covers maximum 16 logs that consist of 8 for
* data and 8 for node logs.
*/
#define NR_CURSEG_DATA_TYPE (3)
#define NR_CURSEG_NODE_TYPE (3)
#define NR_CURSEG_TYPE (NR_CURSEG_DATA_TYPE + NR_CURSEG_NODE_TYPE)
enum {
CURSEG_HOT_DATA = 0, /* directory entry blocks */
CURSEG_WARM_DATA, /* data blocks */
CURSEG_COLD_DATA, /* multimedia or GCed data blocks */
CURSEG_HOT_NODE, /* direct node blocks of directory files */
CURSEG_WARM_NODE, /* direct node blocks of normal files */
CURSEG_COLD_NODE, /* indirect node blocks */
NO_CHECK_TYPE,
};
“`
# 多路日志的