我在伪分布式模式下运行 Hadoop 1.2.1，在同一虚拟机上同时拥有 namenode 和 datanode。数据节点有 4 个卷。我正在做一些关于在 Hadoop 中使用非常小的块大小（4k、8k、...）的测试。复制因子设置为 1。
将块大小设置为 8k 时，我可以使用以下命令将 64MB 文件复制到 hdfs：
bin/hadoop fs -put my64mbfile .
虽然在运行命令时我多次收到以下异常：
13/08/29 10:50:47 WARN hdfs.DFSClient: NotReplicatedYetException sleeping
/user/myuser/my64mbfile retries left 4
13/08/29 10:50:48 INFO hdfs.DFSClient: org.apache.hadoop.ipc.RemoteException:
org.apache.hadoop.hdfs.server.namenode.NotReplicatedYetException:
Not replicated yet:/user/myuser/my64mbfile
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock
(FSNamesystem.java:1905)
at org.apache.hadoop.hdfs.server.namenode.NameNode.addBlock
(NameNode.java:783)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke
(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:587)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1432)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1428)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.
java:1190)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1426)
at org.apache.hadoop.ipc.Client.call(Client.java:1113)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:229)
at com.sun.proxy.$Proxy1.addBlock(Unknown Source)
at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke
(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod
(RetryInvocationHandler.
java:85)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke
(RetryInvocationHandler.java:62)
at com.sun.proxy.$Proxy1.addBlock(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.locateFollowingBlock
(DFSClient.java:3720)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.nextBlockOutputStream
(DFSClient.java:3580)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.access$2600
(DFSClient.java:2783)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream$DataStreamer.run
(DFSClient.java:3023)
在此之后，我重新格式化并重新启动 hadoop。
当我调用相同的命令，但块大小为 4k 时，我仍然收到上面的警告，最终我收到此错误（仅将大约一半的文件复制到 hdfs 之后）：
13/08/29 11:32:38 WARN hdfs.DFSClient: Error Recovery for
blk_1692157315263473676_1009 bad datanode[0] nodes == null
13/08/29 11:32:38 WARN hdfs.DFSClient: Could not get block locations. Source
file "/user/myuser/my64mbfile" - Aborting...
put: java.io.IOException: java.lang.OutOfMemoryError: Requested array size
exceeds VM limit
13/08/29 11:32:38 ERROR hdfs.DFSClient: Failed to close file
/user/myuser/my64mbfile
org.apache.hadoop.ipc.RemoteException: java.io.IOException:
java.lang.OutOfMemoryError: Requested array size exceeds VM limit
at java.util.Arrays.copyOf(Arrays.java:2271)
at java.io.ByteArrayOutputStream.grow(ByteArrayOutputStream.java:113)
at java.io.ByteArrayOutputStream.ensureCapacity(ByteArrayOutputStream.java:93)
at java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:140)
at java.io.DataOutputStream.writeLong(DataOutputStream.java:224)
at org.apache.hadoop.hdfs.protocol.Block.write(Block.java:134)
at org.apache.hadoop.io.ArrayWritable.write(ArrayWritable.java:98)
at org.apache.hadoop.hdfs.server.namenode.FSEditLog$EditLogFileOutputStream.
write(FSEditLog.java:184)
at org.apache.hadoop.hdfs.server.namenode.FSEditLog.logEdit(FSEditLog.java:
1138)
at org.apache.hadoop.hdfs.server.namenode.FSEditLog.logOpenFile(FSEditLog.
java:1299)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.persistBlocks
(FSDirectory.java:305)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock
(FSNamesystem.java:1947)
at org.apache.hadoop.hdfs.server.namenode.NameNode.addBlock(NameNode.java:783)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke
(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:587)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1432)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1428)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.
java:1190)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1426)
at org.apache.hadoop.ipc.Client.call(Client.java:1113)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:229)
at com.sun.proxy.$Proxy1.addBlock(Unknown Source)
at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessor
Impl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod
(RetryInvocationHandler.java:85)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke
(RetryInvocationHandler.java:62)
at com.sun.proxy.$Proxy1.addBlock(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.locateFollowingBlock
(DFSClient.java:3720)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.nextBlockOutputStream
(DFSClient.java:3580)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.access$2600
(DFSClient.java:2783)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream$DataStreamer.run
(DFSClient.java:3023)
数据节点可以处理的块数量是否有限制？或者关于对象数量的名称节点是否有另一个限制（除了 dfs.namenode.fs-limits.max-blocks-per-file）？
对于 4k 的情况，块的总数应该是 16384 个块，这意味着每个卷约 4100 个块，这意味着每个卷约 8200 个文件（包括元数据文件）。