Shulou(Shulou.com)06/01 Report--

This article is about how to store copies in namenode. The editor thinks it is very practical, so I share it with you. I hope you can get something after reading this article. Let's take a look at it with the editor.

The default layout strategy for Hadoop is to put the first copy on the node on which the client is running, and randomly select a node if the client is running outside the cluster, but the system avoids picking nodes that are too full or too busy. The second copy is placed on a node in the rack that is different from the first and randomly selected (off the shelf). The third copy is placed on the same rack as the second copy, and another node is randomly selected. Other copies are placed on randomly selected nodes in the cluster, but the system tries to avoid putting too many copies on the same rack.

Once the location of the copy is selected, a pipeline is created based on the network topology, and if the copy is 3, there is a pipeline as shown in the figure.

Overall, this approach not only provides good stability (data blocks are stored in two racks) but also achieves good attachment balancing, including write bandwidth (write operations need to traverse only one switch), read performance (reads can be selected from two racks) and uniform distribution of blocks in the cluster (clients write only one block on the local rack).

The above is how to store copies in namenode. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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