Could not obtain block

这是错误细节：同样的信息按顺序出现了
0 1 2 3
一共4次，数字在红色的0那里做变化。机器一共5台5个都做了datanode，请高人指点~~谢谢


Error initializing attempt_201001160557_0002_m_000003_
0
:
java.io.IOException: Could not obtain block: blk_-4018899508397085026_1005 file=/nutch/filesystem/mapreduce/system/job_201001160557_0002/job.xml
at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.chooseDataNode(DFSClient.java:1707)
at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.blockSeekTo(DFSClient.java:1535)
at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.read(DFSClient.java:1662)
at java.io.DataInputStream.read(DataInputStream.java:83)
at org.apache.hadoop.io.IOUtils.copyBytes(IOUtils.java:47)
at org.apache.hadoop.io.IOUtils.copyBytes(IOUtils.java:85)
at org.apache.hadoop.fs.FileUtil.copy(FileUtil.java:209)
at org.apache.hadoop.fs.FileUtil.copy(FileUtil.java:142)
at org.apache.hadoop.fs.FileSystem.copyToLocalFile(FileSystem.java:1214)
at org.apache.hadoop.fs.FileSystem.copyToLocalFile(FileSystem.java:1195)
at org.apache.hadoop.mapred.TaskTracker.localizeJob(TaskTracker.java:750)
at org.apache.hadoop.mapred.TaskTracker.startNewTask(TaskTracker.java:1656)
at org.apache.hadoop.mapred.TaskTracker.access$1200(TaskTracker.java:102)
at org.apache.hadoop.mapred.TaskTracker$TaskLauncher.run(TaskTracker.java:1621)

attempt_201001160557_0002_m_000003_*，*那里是map task的尝试运行次数，默认4次不成就告失败。
应该是datanode没连上，可能挂了。
看这里
http://www.aboutyun.com/thread-4861-1-1.html