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https://issues.apache.org/jira/browse/HDFS-13762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16801880#comment-16801880
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Feilong He commented on HDFS-13762:
-----------------------------------

I just uploaded SCMCacheDesign-2019-03-26.pdf. This design doc was updated to 
align with our current implementation. We also added some future plans on HDFS 
SCM cache. Please refer to this doc for more easily understanding our 
implementation.

In addition, currently we are working on this jira's subtask HDFS-14355. You 
can go there to review our patch. Suggestions are always welcome. Thanks!

> Support non-volatile storage class memory(SCM) in HDFS cache directives
> -----------------------------------------------------------------------
>
>                 Key: HDFS-13762
>                 URL: https://issues.apache.org/jira/browse/HDFS-13762
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: caching, datanode
>            Reporter: Sammi Chen
>            Assignee: Feilong He
>            Priority: Major
>         Attachments: HDFS-13762.000.patch, HDFS-13762.001.patch, 
> HDFS-13762.002.patch, HDFS-13762.003.patch, HDFS-13762.004.patch, 
> HDFS-13762.005.patch, HDFS-13762.006.patch, HDFS-13762.007.patch, 
> HDFS-13762.008.patch, SCMCacheDesign-2018-11-08.pdf, 
> SCMCacheDesign-2019-3-26.pdf, SCMCacheTestPlan.pdf
>
>
> No-volatile storage class memory is a type of memory that can keep the data 
> content after power failure or between the power cycle. Non-volatile storage 
> class memory device usually has near access speed as memory DIMM while has 
> lower cost than memory.  So today It is usually used as a supplement to 
> memory to hold long tern persistent data, such as data in cache. 
> Currently in HDFS, we have OS page cache backed read only cache and RAMDISK 
> based lazy write cache.  Non-volatile memory suits for both these functions. 
> This Jira aims to enable storage class memory first in read cache. Although 
> storage class memory has non-volatile characteristics, to keep the same 
> behavior as current read only cache, we don't use its persistent 
> characteristics currently.  
>  
>  
>  



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