Programs released under this license can be used at no cost for both personal and commercial purposes. Open Source software is software with source code that anyone can inspect, modify or enhance. Freeware products can be used free of charge for both personal and professional (commercial use). Please refer “Centralized Cache Management” guide for more details.Freeware programs can be downloaded used free of charge and without any time limitations. Once the InputStream is created, DataNode will send the cached data to the client. When DataNode receives a data read request from a client, if the corresponding block is cached into SCM, DataNode will instantiate an InputStream with the block location path on SCM (pure java implementation) or cache address on SCM (PMDK based implementation). Consistent with DRAM cache, SCM cache also has no cache eviction mechanism. If multiple SCM volumes are configured, a round-robin policy is used to select an available volume for caching a block. Then, build Hadoop with PMDK support by referring to “PMDK library build options” section in `BUILDING.txt` in the source code. To enable PMDK based implementation, user should install PMDK library by referring to the official site. If PMDK native libs could be loaded, it will use PMDK based implementation otherwise it will fallback to java code implementation. The latter implementation can bring user better performance gain in cache write and cache read. There are two implementations for HDFS SCM Cache, one is pure java code implementation and the other is native PMDK based implementation. And all HDFS cache directives keep unchanged. To enable SCM cache, user just needs to configure SCM volume for property “.dirs” in hdfs-site.xml. Non-volatile storage class memory (SCM, also known as persistent memory) is supported in HDFS cache. Running Applications in Docker Containersīackport HDFS persistent memory read cache support to branch-3.2**.
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