一、快照机制snapshots

简单在hbase上做个表做测试：

hbase(main):044:0> scan 'student'
ROW                             COLUMN+CELL                                                                               
 num1                           column=shuxing:name, timestamp=1412189531346, value=jaybing                               
 num2                           column=shuxing:name, timestamp=1412189623682, value=jaychou                               
 num3                           column=shuxing:like, timestamp=1412189669404, value=game                                  
3 row(s) in 0.0260 seconds

创建这个表的快照：
hbase(main):045:0> snapshot 'student','snapshot_student'
0 row(s) in 1.2620 seconds

[root@nn ~]# hadoop fs -ls /tmpdir/
Found 9 items
drwxr-xr-x   - root supergroup          0 2014-10-02 02:58 /tmpdir/.hbase-snapshot
drwxr-xr-x   - root supergroup          0 2014-10-01 21:48 /tmpdir/.tmp
drwxr-xr-x   - root supergroup          0 2014-10-01 21:37 /tmpdir/WALs
drwxr-xr-x   - root supergroup          0 2014-10-02 02:42 /tmpdir/archive
drwxr-xr-x   - root supergroup          0 2014-09-28 00:42 /tmpdir/corrupt
drwxr-xr-x   - root supergroup          0 2014-09-26 11:20 /tmpdir/data
-rw-r--r--   2 root supergroup         42 2014-09-26 11:20 /tmpdir/hbase.id
-rw-r--r--   2 root supergroup          7 2014-09-26 11:20 /tmpdir/hbase.version
drwxr-xr-x   - root supergroup          0 2014-10-02 02:48 /tmpdir/oldWALs
[root@nn ~]# hadoop fs -ls /tmpdir/.hbase-snapshot
Found 2 items
drwxr-xr-x   - root supergroup          0 2014-10-02 02:58 /tmpdir/.hbase-snapshot/.tmp
drwxr-xr-x   - root supergroup          0 2014-10-02 02:58 /tmpdir/.hbase-snapshot/snapshot_student    这应该就是快照的数据文件；

删除student表两行，模拟数据文件损坏；

hbase(main):061:0> disable 'student'
0 row(s) in 2.0310 seconds

hbase(main):062:0> is_
is_a?         is_disabled   is_enabled
hbase(main):062:0> is_enabled 'student'
false                                                                                                                     
0 row(s) in 0.0800 seconds

hbase(main):063:0> drop
drop             drop_all         drop_namespace
hbase(main):063:0> drop 'student'
0 row(s) in 0.1940 seconds

hbase(main):064:0> list

TABLE                                                                                                                     
0 row(s) in 0.0200 seconds

=> []

用快照恢复表：

hbase(main):070:0> restore_snapshot 'snapshot_student'
0 row(s) in 6.4950 seconds

hbase(main):071:0> scan 'student'
ROW                             COLUMN+CELL                                                                               
 num1                           column=shuxing:name, timestamp=1412189531346, value=jaybing                               
 num2                           column=shuxing:name, timestamp=1412189623682, value=jaychou                               
 num3                           column=shuxing:like, timestamp=1412189669404, value=game                                  
3 row(s) in 0.2190 seconds

注： 快照只是保存着快照时hbase表那一刻的数据，至于快照以后的增量的数据，快照是 不支持的；

二、导出表Export

HBase的表导出工具是一个内置的功能，它使数据很容易从hbase导入hdfs目录下的sequencefiles文件，它创造了一个Map reduce任务，通过一系列的hbase api来调用集群，获取指定的表格的每一行数据，并将数据写入指定 的HDFS目录中；

........

三、拷贝表copytable

HBase的表拷贝工具和导出工具差不多，拷贝表也hbase api创建map reduce任务，从源数据读取数据，不同的是拷贝的输出是hbase 的另一个表；这个表可在本地集群，也可在远程集群；