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https://issues.apache.org/jira/browse/HDFS-11505?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15898544#comment-15898544
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Andrew Wang commented on HDFS-11505:
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Hi Kai,
Your understanding is correct. However, I think the vast majority of EC writes
will happen by inheriting the policy from a parent directory at create time, so
usage will be transparent. It's likely that only command-line users will be
calling the setPolicy API, so they'll (hopefully) get nice error messages about
what's an invalid or disabled policy and how to enable policies. As a reference
point, I don't think we've seen a similar need for the storage policy APIs.
Apps like HBase or Hive have often depended on admins setting up
directory-level policies (e.g. storage policies, encryption).
However, if you think having a default policy is important, we could add a
client-side config similar to {{dfs.replication}} to specify a default policy.
Alternatively, this could also be set in NN configuration and queried via
getServerDefaults. As per above though, I'd hope that dir-level policies are
the best fit for users who want a simple way of using EC.
> Do not enable any erasure coding policies by default
> ----------------------------------------------------
>
> Key: HDFS-11505
> URL: https://issues.apache.org/jira/browse/HDFS-11505
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: erasure-coding
> Affects Versions: 3.0.0-alpha3
> Reporter: Andrew Wang
> Assignee: Manoj Govindassamy
> Labels: hdfs-ec-3.0-must-do
>
> As discussed on HDFS-11314, administrators need to choose the correct set of
> EC policies based on cluster size and desired fault-tolerance properties.
> This means we should not enable any EC policies by default, since any default
> value could be incorrect.
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