HDFS Quotas Guide（HDFS配额指南）

HDFS Quotas Guide官网链接2.9.2版本
HDFS Quotas Guide官网链接2.7.1版本

简介：Hadoop提供两种配额（quota）模式，name quota和space quota。name quota限制路径的文件（含文件夹）数目，space quota限制的”磁盘”占用空间。可以通过此功能实现团队的存储使用管理。

• Set the name quota to be N for each directory. Best effort for each directory, with faults reported if N is not a positive long integer, the directory does not exist or it is a file, or the directory would immediately exceed the new quota.
  $ hadoop dfsadmin -setQuota <max_number> <directory>
• Remove any name quota for each directory. Best effort for each directory, with faults reported if the directory does not exist or it is a file. It is not a fault if the directory has no quota.
  $ hadoop dfsadmin -setSpaceQuota <max_size> <directory>
• Remove any name quota for each directory. Best effort for each directory, with faults reported if the directory does not exist or it is a file. It is not a fault if the directory has no quota.
  $ hadoop dfsadmin -clrQuota <directory>
• Remove any space quota for each directory. Best effort for each directory, with faults reported if the directory does not exist or it is a file. It is not a fault if the directory has no quota.
  $ hadoop dfsadmin -clrSpaceQuota <directory>

Name Quota示例

首先测试name quota，进行如下操作：

• 准备hdfs路径，设置name quota，文件数量限制为5

$hdfs dfs -mkdir /name_quota
$hdfs dfsadmin -setQuota 5 /name_quota

$touch 1
$hdfs dfs -copyFromLocal 1 /name_quota/1
$hdfs dfs -copyFromLocal 1 /name_quota/2
$hdfs dfs -copyFromLocal 1 /name_quota/3
$hdfs dfs -copyFromLocal 1 /name_quota/4
$hdfs dfs -copyFromLocal 1 /name_quota/5
copyFromLocal: The NameSpace quota (directories and files) of directory
/name_quota is exceeded: quota=5 file count=6

创建一个临时文件“1“，并将它复制到指定hdfs路径下，发现，当复制到第5个时失败，提示显示达到quota限制，说明quota生效，同时，我们设置quota_max_num为5，但只放了4个文件就满了，说明这个数字限制是包含文件夹的。
实际上是可以理解的，在HDFS中，无论文件和文件夹的基本抽象是一样的，占用基本同样的元数据信息，name quota实际上是元数据信息的配额。

Space Quota示例

• 创建测试路径并设置space quota

$hdfs dfs -mkdir /space_quota
$hdfs dfsadmin -setSpaceQUota 50m /space_quota

$mkfile 10m 10m
$hdfs dfs -copyFromLocal 10m /space_quota/10m_1

利用mkfile命令创建一个大小10m的文件（我用的是Mac，Linux系统使用dd命令创建指定大小文件），预期是在这个hdfs路径下可以存放5个10m的文件，第六个会超出，但实际情况是，第一个就失败了，报错如下：
Caused by: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.protocol.DSQuotaExceededException): The DiskSpace quota of /space_quota is exceeded: quota = 52428800 B = 50 MB but diskspace consumed = 134217728 B = 128 MB
看提示就理解，因为HDFS是以block为单位进行实际存储的，对于一个10m的文件，仍然会打成一个block存储，我的HDFS block size是128m，所以space quota配置50m，一个block也放不下，自然失败，因此进行一下改动，重新设置：

$hdfs dfsadmin -setSpaceQUota 1024m /space_quota
$mkfile 128m 128m
$ hdfs dfs -copyFromLocal 128m /space_quota/128m_1
$ hdfs dfs -copyFromLocal 128m /space_quota/128m_2
$ hdfs dfs -copyFromLocal 128m /space_quota/128m_3
$ hdfs dfs -copyFromLocal 128m /space_quota/128m_4
$ hdfs dfs -copyFromLocal 128m /space_quota/128m_5
$ hdfs dfs -copyFromLocal 128m /space_quota/128m_6
$ hdfs dfs -copyFromLocal 128m /space_quota/128m_7
$ hdfs dfs -copyFromLocal 128m /space_quota/128m_8
$ hdfs dfs -copyFromLocal 128m /space_quota/128m_9

1024m的配额，可以放8个128m文件，在放第九个时，报错，核心信息如下：

18/05/18 16:13:01 WARN hdfs.DFSClient: DataStreamer Exception org.apache.hadoop.hdfs.protocol.DSQuotaExceededException: The DiskSpace quota of /space_quota is exceeded: quota = 1073741824 B = 1 GB but diskspace consumed = 1207959552 B = 1.13 GB
符合预期，成功限制了规定路径下的存储空间配额。

另外，经过测试（示例不详述），name quota和space quota可以同时作用于同一路径。

标签：hdfs,name,HDFS,space,quota,dfs,Quotas,128m,Guide
来源： https://blog.51cto.com/u_15278282/2933728