hadoop不适合小文件的存储，小文件本省就占用了很多的metadata，就会造成namenode越来越大。Hadoop Archives的出现视为了缓解大量小文件消耗namenode内存的问题。
采用ARCHIVE 不会减少 文件存储大小，只会压缩NAMENODE 的空间使用
Hadoop档案指南
概述
Hadoop存档是特殊格式的存档。Hadoop存档映射到文件系统目录。Hadoop归档文件总是带有* .har扩展名
Hadoop存档目录包含元数据（采用_index和_masterindex形式）
数据部分data（part- *）文件。
_index文件包含归档文件的名称和部分文件中的位置。
如何创建档案
用法：hadoop archive -archiveName 归档名称 -p 父目录 [-r <复制因子>] 原路径（可以多个） 目的路径
-archivename是您想要创建的档案的名称。一个例子是foo.har。该名称应该有一个* .har扩展名。父参数是指定文件应归档到的相对路径。例子是：
hadoop archive -archiveName foo.har -p /foo/bar -r 3 a b c /user/hz
执行该命令后，原输入文件不会被删除，需要手动删除
hadoop fs -rmr /foo/bar/a
hadoop fs -rmr /foo/bar/b
hadoop fs -rmr /foo/bar/c
这里/ foo / bar是父路径，a b c (路径用空格隔开，可以配置多个)是父路径的相对路径。请注意，这是一个创建档案的Map / Reduce作业。你需要一个map reduce集群来运行它。
-r表示期望的复制因子; 如果未指定此可选参数，则将使用复制因子10。
目的存档一个目录/user/hz
如果您指定加密区域中的源文件，它们将被解密并写入存档。如果har文件不在加密区中，则它们将以清晰（解密）的形式存储。如果har文件位于加密区域，它们将以加密形式存储。
例子：
###########################################################################################
[admin@cdn3 ~]$ hadoop archive -archiveName test3.har -p /user/admin -r 3 oozie-oozi /user/admin
18/03/19 16:18:33 INFO impl.TimelineClientImpl: Timeline service address: http://cnn1.sctel.com:8188/ws/v1/timeline/
18/03/19 16:18:33 INFO client.RMProxy: Connecting to ResourceManager at cnn1.sctel.com/192.168.2.244:8050
18/03/19 16:18:34 INFO impl.TimelineClientImpl: Timeline service address: http://cnn1.sctel.com:8188/ws/v1/timeline/
18/03/19 16:18:34 INFO client.RMProxy: Connecting to ResourceManager at cnn1.sctel.com/192.168.2.244:8050
18/03/19 16:18:35 INFO impl.TimelineClientImpl: Timeline service address: http://cnn1.sctel.com:8188/ws/v1/timeline/
18/03/19 16:18:35 INFO client.RMProxy: Connecting to ResourceManager at cnn1.sctel.com/192.168.2.244:8050
18/03/19 16:18:35 INFO hdfs.DFSClient: Created HDFS_DELEGATION_TOKEN token 2461 for admin on 192.168.2.244:8020
18/03/19 16:18:35 INFO security.TokenCache: Got dt for hdfs://cnn1.sctel.com:8020; Kind: HDFS_DELEGATION_TOKEN, Service: 192.168.2.244:8020, Ident: (HDFS_DELEGATION_TOKEN token 2461 for admin)
18/03/19 16:18:35 INFO mapreduce.JobSubmitter: number of splits:1
18/03/19 16:18:36 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1519809200150_0029
18/03/19 16:18:36 INFO mapreduce.JobSubmitter: Kind: HDFS_DELEGATION_TOKEN, Service: 192.168.2.244:8020, Ident: (HDFS_DELEGATION_TOKEN token 2461 for admin)
18/03/19 16:18:37 INFO impl.YarnClientImpl: Submitted application application_1519809200150_0029
18/03/19 16:18:37 INFO mapreduce.Job: The url to track the job: http://cnn1.sctel.com:8088/proxy/application_1519809200150_0029/
18/03/19 16:18:37 INFO mapreduce.Job: Running job: job_1519809200150_0029
18/03/19 16:18:51 INFO mapreduce.Job: Job job_1519809200150_0029 running in uber mode : false
18/03/19 16:18:51 INFO mapreduce.Job: map 0% reduce 0%
18/03/19 16:19:05 INFO mapreduce.Job: map 100% reduce 0%
18/03/19 16:19:14 INFO mapreduce.Job: map 100% reduce 100%
18/03/19 16:19:15 INFO mapreduce.Job: Job job_1519809200150_0029 completed successfully
18/03/19 16:19:15 INFO mapreduce.Job: Counters: 49
File System Counters
FILE: Number of bytes read=2405
FILE: Number of bytes written=286331
FILE: Number of read operations=0
FILE: Number of large read operations=0
FILE: Number of write operations=0
HDFS: Number of bytes read=694282
HDFS: Number of bytes written=694279
HDFS: Number of read operations=34
HDFS: Number of large read operations=0
HDFS: Number of write operations=7
Job Counters
Launched map tasks=1
Launched reduce tasks=1
Other local map tasks=1
Total time spent by all maps in occupied slots (ms)=24348
Total time spent by all reduces in occupied slots (ms)=12302
Total time spent by all map tasks (ms)=12174
Total time spent by all reduce tasks (ms)=6151
Total vcore-seconds taken by all map tasks=12174
Total vcore-seconds taken by all reduce tasks=6151
Total megabyte-seconds taken by all map tasks=18699264
Total megabyte-seconds taken by all reduce tasks=12597248
Map-Reduce Framework
Map input records=18
Map output records=18
Map output bytes=2357
Map output materialized bytes=2405
Input split bytes=98
Combine input records=0
Combine output records=0
Reduce input groups=18
Reduce shuffle bytes=2405
Reduce input records=18
Reduce output records=0
Spilled Records=36
Shuffled Maps =1
Failed Shuffles=0
Merged Map outputs=1
GC time elapsed (ms)=315
CPU time spent (ms)=6760
Physical memory (bytes) snapshot=1349992448
Virtual memory (bytes) snapshot=4604309504
Total committed heap usage (bytes)=1558183936
Shuffle Errors
BAD_ID=0
CONNECTION=0
IO_ERROR=0
WRONG_LENGTH=0
WRONG_MAP=0
WRONG_REDUCE=0
File Input Format Counters
Bytes Read=2208
File Output Format Counters
Bytes Written=0
###################################################################################################
查看生成的文件：
如何在档案中查找文件
该档案将自己公开为文件系统层。因此，档案中的所有fs shell命令都可以工作，但使用不同的URI。另外，请注意档案是不可变的。所以，重命名，删除并创建返回一个错误。Hadoop Archives的URI是
HAR：//方案-主机名：端口/ archivepath / fileinarchive
如果没有提供方案，它假定底层文件系统。在这种情况下，URI看起来像
HAR：/// archivepath / fileinarchive
查询：
hadoop fs -ls har:/user/admin/test3.har
hadoop fs -ls -R har:/user/admin/test3.har
如何解除归档
由于档案中的所有fs shell命令都是透明的，因此取消存档只是复制的问题。
依次取消存档：
hadoop fs -cp har:/user/admin/test3.har /user/admin/oo
要并行解压缩，请使用DistCp：
hadoop distcp har:/user/admin/test3.har /user/admin/oo2
##################################################################################################################################
[admin@cdn3 ~]$ hadoop distcp har:/user/admin/test3.har /user/admin/oo2
18/03/19 16:42:49 INFO tools.DistCp: Input Options: DistCpOptions{atomicCommit=false, syncFolder=false, deleteMissing=false, ignoreFailures=false, maxMaps=20, sslConfigurationFile='null', copyStrategy='uniformsize', sourceFileListing=null, sourcePaths=[har:/user/admin/test3.har], targetPath=/user/admin/oo2, targetPathExists=false, preserveRawXattrs=false}
18/03/19 16:42:50 INFO impl.TimelineClientImpl: Timeline service address: http://cnn1.sctel.com:8188/ws/v1/timeline/
18/03/19 16:42:50 INFO client.RMProxy: Connecting to ResourceManager at cnn1.sctel.com/192.168.2.244:8050
18/03/19 16:42:51 INFO hdfs.DFSClient: Created HDFS_DELEGATION_TOKEN token 2462 for admin on 192.168.2.244:8020
18/03/19 16:42:51 INFO security.TokenCache: Got dt for har:/user/admin/test3.har; Kind: HDFS_DELEGATION_TOKEN, Service: 192.168.2.244:8020, Ident: (HDFS_DELEGATION_TOKEN token 2462 for admin)
18/03/19 16:42:52 INFO impl.TimelineClientImpl: Timeline service address: http://cnn1.sctel.com:8188/ws/v1/timeline/
18/03/19 16:42:52 INFO client.RMProxy: Connecting to ResourceManager at cnn1.sctel.com/192.168.2.244:8050
18/03/19 16:42:52 INFO mapreduce.JobSubmitter: number of splits:8
18/03/19 16:42:53 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1519809200150_0030
18/03/19 16:42:53 INFO mapreduce.JobSubmitter: Kind: HDFS_DELEGATION_TOKEN, Service: 192.168.2.244:8020, Ident: (HDFS_DELEGATION_TOKEN token 2462 for admin)
18/03/19 16:42:54 INFO impl.YarnClientImpl: Submitted application application_1519809200150_0030
18/03/19 16:42:54 INFO mapreduce.Job: The url to track the job: http://cnn1.sctel.com:8088/proxy/application_1519809200150_0030/
18/03/19 16:42:54 INFO tools.DistCp: DistCp job-id: job_1519809200150_0030
18/03/19 16:42:54 INFO mapreduce.Job: Running job: job_1519809200150_0030
18/03/19 16:43:11 INFO mapreduce.Job: Job job_1519809200150_0030 running in uber mode : false
18/03/19 16:43:11 INFO mapreduce.Job: map 0% reduce 0%
18/03/19 16:43:23 INFO mapreduce.Job: map 25% reduce 0%
18/03/19 16:43:25 INFO mapreduce.Job: map 50% reduce 0%
18/03/19 16:43:27 INFO mapreduce.Job: map 63% reduce 0%
18/03/19 16:43:28 INFO mapreduce.Job: map 75% reduce 0%
18/03/19 16:43:29 INFO mapreduce.Job: map 100% reduce 0%
18/03/19 16:43:30 INFO mapreduce.Job: Job job_1519809200150_0030 completed successfully
18/03/19 16:43:30 INFO mapreduce.Job: Counters: 33
File System Counters
FILE: Number of bytes read=0
FILE: Number of bytes written=1135544
FILE: Number of read operations=0
FILE: Number of large read operations=0
FILE: Number of write operations=0
HDFS: Number of bytes read=717982
HDFS: Number of bytes written=691976
HDFS: Number of read operations=266
HDFS: Number of large read operations=0
HDFS: Number of write operations=40
Job Counters
Launched map tasks=8
Other local map tasks=8
Total time spent by all maps in occupied slots (ms)=86922
Total time spent by all reduces in occupied slots (ms)=0
Total time spent by all map tasks (ms)=86922
Total vcore-seconds taken by all map tasks=86922
Total megabyte-seconds taken by all map tasks=89008128
Map-Reduce Framework
Map input records=18
Map output records=0
Input split bytes=928
Spilled Records=0
Failed Shuffles=0
Merged Map outputs=0
GC time elapsed (ms)=681
CPU time spent (ms)=14030
Physical memory (bytes) snapshot=1731399680
Virtual memory (bytes) snapshot=16419467264
Total committed heap usage (bytes)=2720006144
File Input Format Counters
Bytes Read=6654
File Output Format Counters
Bytes Written=0
org.apache.hadoop.tools.mapred.CopyMapper$Counter
BYTESCOPIED=691976
BYTESEXPECTED=691976
COPY=18
[admin@cdn3 ~]$ hadoop fs -ls /user/admin/oo2
Found 1 items
drwxr-x--- - admin default 0 2018-03-19 16:43 /user/admin/oo2/oozie-oozi
################################################################################################################