创建lvname名为snaplvname,大小为20M的新快照卷 A: lvcreate –nsnaplv–L20M/dev/vgname/lvname B: lvcreate–s–nsnaplv–L20M/dev/vgname/lvname C: mount –ro /dev/vgname/snaplv D: lvcreate–ssnaplv–L20M/dev/vgname/lvname