在ZFS中,有一个’拷贝’属性应该具有这种效果. BTRFS wiki页面列出了“文件镜像”功能.但这是指完整数据镜像还是实际基于每个文件？
If everything is RAID-1 (or RAID-0,or in general all the same RAID level),then yes,we could give a sane and consistent value from df. However,we have plans to allow per-subvolume and per-file RAID levels. In this case,it becomes impossible to give a sensible estimate as to how much space there is left.
如果你现在需要这个功能,ZFS on Linux非常稳定(在完成的功能和思想共享方面可能是更好的选择).
