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https://issues.apache.org/jira/browse/HDFS-8401?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14563580#comment-14563580
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Andrew Wang commented on HDFS-8401:
-----------------------------------
bq. It's impractical to involve the administrator every time a new file is to
be cached.
Read caching can be done by normal users, not just admins. We also have
directory-level cache directives which kick in automatically without any
explicit user involvement
If some of the other enhancements you mention could be built into HDFS, that'd
also be preferable (de-dupe, predictability (?)).
Anecdotal, but I've heard a lot of users say that changing the scheme is not an
option for them. If your concern is ease of use, focusing on improvements to
what we already have in HDFS might be more bang for the buck. We have the
LAZY_PERSIST storage policy and directory-level cache directives which seem
like a start. Colin also mentioned opportunistic cache directives, which would
be a really nice enhancement.
> Memfs - a layered file system for in-memory storage in HDFS
> -----------------------------------------------------------
>
> Key: HDFS-8401
> URL: https://issues.apache.org/jira/browse/HDFS-8401
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Arpit Agarwal
> Assignee: Arpit Agarwal
>
> We propose creating a layered filesystem that can provide in-memory storage
> using existing features within HDFS. memfs will use lazy persist writes
> introduced by HDFS-6581. For reads, memfs can use the Centralized Cache
> Management feature introduced in HDFS-4949 to load hot data to memory.
> Paths in memfs and hdfs will correspond 1:1 so memfs will require no
> additional metadata and it can be implemented entirely as a client-side
> library.
> The advantage of a layered file system is that it requires little or no
> changes to existing applications. e.g. Applications can use something like
> {{memfs://}} instead of {{hdfs://}} for files targeted to memory storage.
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