I haven't checked the code for any special cases of replication = 1. The write a block sequence is:
1. Get a list of datanodes from the namenode for the block replicas, the reqest host being the first datanode returned if the request host is a datanode. 2. send the block with the list of datanodes to receive it to the first datanode in the list 3. That datanode sends the block to the next 4. 3 repeats until the block is fully replicated. On Thu, Apr 23, 2009 at 2:08 PM, Jerome Banks <jba...@quantcast.com> wrote: > FYI, The pipe v2 results were created with > com.quantcast.armor.jobs.pipev3.util.CountVG , inputing the results from > com.quantcast.armor.jobs.pipev3.util.MyHarvestV2 (the mainline pipev2 > harvest). > The pipe v3 results were a one day run of BloomDaily for 04/12/2009. > The CSV files were generated with TopNFlow. > > > On 4/23/09 1:56 PM, "Amr Awadallah" <a...@cloudera.com> wrote: > > yes, it will be split across many nodes, and if possible each block will > get a different datanode. > > see following link for more details: > > > http://hadoop.apache.org/core/docs/current/hdfs_design.html#Data+Organization > > -- amr > > Alex Loddengaard wrote: > > I believe the blocks will be distributed across data nodes and not local > to > > only one data node. If this wasn't the case, then running a MR job on > the > > file would only be local to one task tracker. > > > > Alex > > > > On Thu, Apr 23, 2009 at 2:14 AM, Xie, Tao <xietao1...@gmail.com> wrote: > > > > > >> If a cluster has many datanodes and I want to copy a large file into > DFS. > >> If the replication number is set to 1, does the namenode will put the > file > >> data on one datanode or several nodes? I wonder if the file will be > split > >> into blocks then different unique blocks are on different datanodes. > >> > >> -- > >> View this message in context: > >> > http://www.nabble.com/The-mechanism-of-choosing-target-datanodes-tp23193235p23193235.html > >> Sent from the Hadoop core-user mailing list archive at Nabble.com. > >> > >> > >> > > > > > > -- Alpha Chapters of my book on Hadoop are available http://www.apress.com/book/view/9781430219422
