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Since HDFS support RAMDisk, what's the advantage by using Alluxio. In our case we are not going to support integrate different type of under storage beside HDFS.

Abdul Hoque Nuri
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Jerome tan
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1 Answers1

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Having the concept of Under Storage and keeping the data and metadata in sync between Alluxio and Under Storage is the key difference between Alluxio and HDFS. Besides, there are still a few other difference as the consequences that Alluxio is designed to host hot data and implements the semantics of a distributed cache whereas HDFS is designed to be a persistent storage service.

  1. Alluxio provides with configurable eviction policies.
  2. Alluxio natively supports operations like setting TTLs (see link).
  3. The number of block copies of data in HDFS is a fixed constant for persistency (3 by default, one can use setrep command to change the replication level in HDFS). However, the number of block replicas in Alluxio can be changed automatically based on the popularity of different blocks. If a block is accessed by multiple different applications on different servers, there can be more copies.
  4. Alluxio supports tiered storage, so one can configure multiple tiers with MEM, SSD and HDD (see link).
apc999
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