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This article introduces the relevant knowledge of "what are the knowledge points of HBase". In the operation of actual cases, many people will encounter such a dilemma. Next, let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

HBase-Hadoop Database is a highly reliable, high-performance, column-oriented and scalable distributed storage system. Large-scale structured storage clusters can be built on cheap PC Server by using HBase technology.

Different from commercial big data products such as FUJITSU Cliq, HBase is an open source implementation of Google Bigtable, similar to Google Bigtable uses GFS as its file storage system, HBase uses Hadoop HDFS as its file storage system; Google runs MapReduce to deal with massive data in Bigtable, HBase also uses Hadoop MapReduce to deal with massive data in HBase; Google Bigtable uses Chubby as a collaborative service and HBase uses Zookeeper as its counterpart.

I. the characteristics of hbase

1. The final persistent storage of hbase data is based on the hsfs file system. The storage capacity is almost unlimited and can be expanded online at any time.

2. The data addition, deletion, modification and query function module of hbase is a distributed system.

3. Nosql database, table structure.

II. Storage of HBase

All data files in HBase are stored on the Hadoop HDFS file system.

1. HFile, the storage format of KeyValue data in HBase. HFile is the binary format file of Hadoop. In fact, StoreFile makes a lightweight package for HFile, that is, the bottom layer of StoreFile is HFile.

2. The storage format of WAL (Write Ahead Log) in HLog File,HBase is physically the Sequence File of Hadoop.

III. The working mechanism of HBase

Detailed analysis of the working mechanism of hbase:

1. The overall working mechanism of hbase is to accept the request command from the client, read the table file information from hdfs and return it to the client.

2. Each hbase server is responsible for the corresponding region area in the table file. The storage of the table file on the hdfs is also divided into separate storage for each region, and storage for multiple column families in each region.

3. There are two roles in hbase cluster. Regionserver and master,regionserver are responsible for responding to client requests and reading table files.

Master is responsible for monitoring the status of regionserver so that the offline regionserver can be processed in time to ensure the normal operation of the hbase cluster. When a region dies, master will monitor it in time. Here, zookeeper is used to manage regionserver status information.

When a master dies, it will not affect the client to check the data, but if the regionserver dies and the master cannot be monitored in time, the data query will be affected. The solution is to set another master, an active status and a standby status as a backup. When the master of the active dies, the master of the standby will change to the active status and monitor the regionserver.

4. Master and zookeeper constitute high availability.

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