Hi Jun,
User can run multiple DataNode instances on same physical server provided user changes the DataNode configuration. One simple test you can try: Copy the DataNode installation to a different folder/directory of same physical server. Change the necessary configuration like dfs.data.dir/http ports etc. Start both the DataNodes. It should run properly. We have tried this for development and testing purpose but, real case this is usually not the scenario. Please visit the following link: http://hadoop.apache.org/common/docs/current/hdfs_design.html The link clearly tells: “The architecture does not preclude running multiple DataNodes on the same machine” Hope it answers your query. :-) Regards, Computers make very fast and accurate mistakes....... This email and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! _____ From: 谭军 [mailto:tanjun_2...@163.com] Sent: Monday, August 08, 2011 2:49 PM To: mapreduce-user@hadoop.apache.org; subroto.san...@huawei.com Subject: Re:RE: Can I use the cores of each CPU to be the datanodes instead of CPU? Hi Subroto, I'm sorry for my poor English. Are you thinking about CPU core to Hadoop process mapping? Maybe this is the issue. 2 computers with 2 CPUs. Each CPU has 2 cores. Now I have 2 physical datanodes. Can I get 4 physical datanodes? I don't know wether I make my point clear? -- Regards! Jun Tan 在 2011-08-08 17:05:31，"Subroto Sanyal" <subrotosan...@huawei.com> 写道： Hi Jun, Sorry, I didn’t get your question properly….. :-( Are you thinking in terms of Virtual Machines running on same physical server? Are you thinking about CPU core to Hadoop process mapping? As per my understanding, Hadoop doesn’t have intelligence of different cores (ideally application should be independent of hardware details) It is possible to run multiple instance of DataNode in same physical server, provide the configurations are different for each DataNode process. Regards, Subroto Sanyal _____ From: 谭军 [mailto:tanjun_2...@163.com] Sent: Monday, August 08, 2011 2:16 PM To: mapreduce Subject: Can I use the cores of each CPU to be the datanodes instead of CPU? Hi, I have 2 computers each of which is double-core CPU. The 2 computers are datanodes and another computer is the namenode. Now, I want to increase the number of datanode but no more computers available. Can I use the 4 cores of the 2 computers to be 4 datanodes? -- Best regards! Jun Tan
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