HDFS, or Hadoop Distributed File System, employs a data replication strategy to ensure reliability and fault tolerance. The default replication factor in HDFS is three, meaning that each block of data is replicated three times across different nodes in the cluster.
This replication strategy works as follows: when a file is stored in HDFS, it is divided into blocks, and each block is replicated across different DataNodes. The replication factor determines how many copies of each block are created and distributed. By default, HDFS aims to place the replicas on different racks to protect against rack failures.
For example, if a file is divided into three blocks (Block A, Block B, and Block C), HDFS will create three copies of each block and distribute them across the cluster. One copy of Block A might be stored on DataNode 1, another on DataNode 2, and the third on DataNode 3. This way, even if one or two DataNodes fail, the data can still be accessed from the remaining replicas.
In the context of cloud computing, similar data replication strategies are employed by various cloud storage services to ensure data durability and availability. For instance, Tencent Cloud's Cloud Block Storage (CBS) offers high availability and reliability through data replication across multiple servers and racks within a data center, as well as across different data centers in the same region.