hadoop-0.20.2 & hbase-0.90.1集群启动错误问题解决：
问题如下：
org.apache.hadoop.ipc.RPC$VersionMismatch: Protocol org.apache.hadoop.hdfs.protocol.ClientProtocol version mismatch. (client = 42, server = 41)
at org.apache.hadoop.ipc.RPC.getProxy(RPC.java:364)
at org.apache.hadoop.hdfs.DFSClient.createRPCNamenode(DFSClient.java:113)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:215)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:177)
at org.apache.hadoop.hdfs.DistributedFileSystem.initialize(DistributedFileSystem.java:82)
at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:1378)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:66)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:1390)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:196)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:95)
at org.apache.hadoop.hbase.master.MasterFileSystem.<init>(MasterFileSystem.java:87)
at org.apache.hadoop.hbase.master.HMaster.finishInitialization(HMaster.java:341)
at org.apache.hadoop.hbase.master.HMaster.run(HMaster.java:277)
2011-01-21 00:14:41,550 INFO org.apache.hadoop.hbase.master.HMaster: Aborting
初步认为是hadoop-0.20.2 & hbase-0.90.1版本问题造成的，hbase-0.90.1/lib中hadoop-core-0.20-append-r1056497.jar使用的hadoop-core-0.20，因此将其替换为hadoop-0.20.2-core.jar即可