because it doesn「t use the file backup flag bit of file system, it is not limited by file system backup function.
由于不使用文件系统的文件备份标志位,因此不受文件系统备份功能的限制。
a flag bit in the status register of the central processing unit used to show a negative result from an arithmetic operation.
中央处理机的状态寄存器中的一个标志位元,用来表示算数运算结果是负数。
if adopting the meta-data snap, when modifying the data in data volume, system only modifies the flag bit that corresponding to data block in bitmap, and doesn」t create real snap.