Garbage collection is the process of reclaiming invalid blocks (those that contain some amount of invalid data).

垃圾收集是一个回收无效块的过程(无效块中包含了一些无效数据)。

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The garbage collector moves valid blocks to the tail of the log, skips invalid or obsolete blocks, and erases them (see Figure 2).

垃圾收集器将有效块移动到日志的尾部，跳过无效或废弃块，并擦除它们（参见图 2）。

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You can detect the presence of back blocks from a failed flash operation (such as an Erase) or an invalid Write operation (discovered through an invalid Error Correction Code, or ECC).

如果 flash 操作（例如 Erase）失败，或者 Write 操作无效（通过无效的错误校正代码发现，Error Correction Code，ECC），那么说明出现了坏块。

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