cephfs snap 快照

前言
Cephfs的快照功能在官网都很少提及，因为即使开发了很多年，但是由于cephfs的复杂性，功能一直没能达到稳定，这里，只是介绍一下这个功能，怎么使用，并且建议不要在生产中使用，因为搞不好是会丢数据的

功能介绍
首先这个功能是默认关闭的，所以需要开启

ceph fs set ceph  allow_new_snaps 1

Error EPERM: Warning! This feature is experimental.It may cause problems up to and including data loss.Consult the documentation at ceph.com, and if unsure, do not proceed.Add --yes-i-really-mean-it if you are certain.

ceph fs set ceph  allow_new_snaps 1  --yes-i-really-mean-it

从提示上可以看到，还是不要在生产上使用

开发者的话：

In Jewel ceph fs snapshots are still experimental. Does someone has a clue when this would become stable, or how experimental this is ?
We’re not sure yet. Probably it will follow stable multi-MDS; we’re thinking about redoing some of the core snapshot pieces still. :/
It’s still pretty experimental in Jewel. Shen had been working on this and I think it often works, but tends to fall apart under the failure of other components (eg, restarting an MDS while snapshot work is happening).
-Greg

挂载集群

[root@lab8106 ~]# mount -t ceph 192.168.8.106:/ /mnt
[root@lab8106 ~]# cd /mnt/

快照是对目录创建的
所以我们来看下

[root@lab8106 mnt]# ll
total 0
drwxr-xr-x 1 root root 51341 Dec 13 11:41 test1
drwxr-xr-x 1 root root 51591 Dec 13 16:18 test2
drwxr-xr-x 1 root root 30951 Dec 13 15:19 test3

创建快照

[root@lab8106 mnt]# mkdir .snap/snap1
[root@lab8106 mnt]# ll .snap/
total 0
drwxr-xr-x 1 root root 133883 Dec 13 14:21 snap1
[root@lab8106 mnt]# ll .snap/snap1
total 0
drwxr-xr-x 1 root root 51341 Dec 13 11:41 test1
drwxr-xr-x 1 root root 51591 Dec 13 16:18 test2
drwxr-xr-x 1 root root 30951 Dec 13 15:19 test3

创建快照很简单，就是在需要做快照的目录下面执行 mkdir .snap/snapname 后面接快照的名称

快照的速度非常快，秒级别的

恢复快照数据

[root@lab8106 mnt]# cp -ra .snap/snap1/* ./

删除快照

[root@lab8106 mnt]# rmdir .snap/snap1

删除快照需要用rmdir命令