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https://issues.apache.org/jira/browse/HDFS-7866?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15129089#comment-15129089
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Zhe Zhang commented on HDFS-7866:
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[~lirui] [~drankye] Thanks for the discussions.
bq. As to policy ID mapping, do you mean we should pre-define the IDs for
system EC policies, like what we do in HdfsConstants for storage policies?
Yes I think we should do this for the current phase. As Kai suggested above,
and quoted Andrew's comment, I think full pluggability is still a pretty remote
target. When we do implement customer-pluggable policies, we should revisit the
issue together with block storage policies.
bq. Maybe 7 bits for EC policies (up to 128 ones) and 4 bits for repl factor
(up to 16 sounds enough for striped blocks).
Well I think this decision can be left open now. Right now we can just use the
11 bits for EC policies, and then decide how many to squeeze for repl factor.
I've seen some special cases where the repl factor of some contiguous blocks
are tuned high so all DNs in the cluster will have them. But for striped
blocks, maybe that's not a requirement anymore. So 16 might be OK.
> Erasure coding: NameNode manages multiple erasure coding policies
> -----------------------------------------------------------------
>
> Key: HDFS-7866
> URL: https://issues.apache.org/jira/browse/HDFS-7866
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Kai Zheng
> Assignee: Rui Li
> Attachments: HDFS-7866-v1.patch, HDFS-7866-v2.patch,
> HDFS-7866-v3.patch, HDFS-7866.4.patch, HDFS-7866.5.patch, HDFS-7866.6.patch,
> HDFS-7866.7.patch
>
>
> This is to extend NameNode to load, list and sync predefine EC schemas in
> authorized and controlled approach. The provided facilities will be used to
> implement DFSAdmin commands so admin can list available EC schemas, then
> could choose some of them for target EC zones.
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