23，lvm 快照

1，lvm 快照
[root@centos7 ~]# lvs
  LV   VG       Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root centos   -wi-ao----   9.30g                                                    
  swap centos   -wi-ao---- 512.00m                                                    
  lv1  vg1_demo -wi-a-----  40.00m                                                    
[root@centos7 ~]# 
[root@centos7 ~]# vgs
  VG       #PV #LV #SN Attr   VSize VFree
  centos     1   2   0 wz--n- 9.80g    0 
  vg1_demo   3   1   0 wz--n- 2.50g 2.46g
[root@centos7 ~]# 
[root@centos7 ~]# pvs
  PV         VG       Fmt  Attr PSize  PFree 
  /dev/sda2  centos   lvm2 a--   9.80g     0 
  /dev/sdb6  vg1_demo lvm2 a--  48.00m 48.00m
  /dev/sdb7  vg1_demo lvm2 a--  48.00m 48.00m
  /dev/sdb8  vg1_demo lvm2 a--  <2.41g <2.37g
[root@centos7 ~]# 
[root@centos7 ~]# lvcreate -n lvs_snap -L 45M -s /dev/vg1_demo/lv1 
  Using default stripesize 64.00 KiB.
  Rounding up size to full physical extent 48.00 MiB
  Reducing COW size 48.00 MiB down to maximum usable size 44.00 MiB.
  Logical volume "lvs_snap" created.
[root@centos7 ~]# 
[root@centos7 ~]# lvs
  LV       VG       Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root     centos   -wi-ao----   9.30g                                                    
  swap     centos   -wi-ao---- 512.00m                                                    
  lv1      vg1_demo owi-a-s---  40.00m                                                    
  lvs_snap vg1_demo swi-a-s---  44.00m      lv1    0.00                                   
[root@centos7 ~]# 

2，快照可以直接挂载。和原始的文件对比，比对区别