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https://issues.apache.org/jira/browse/HDFS-7866?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15066031#comment-15066031
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Rui Li commented on HDFS-7866:
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Thanks Kai for your comments.
bp. However, please don't set it as default policy or change the default policy
at all.
Yeah I didn't mean to change the default policy. The change in the patch is
temporary to make the tests pick the new policy.
bp. Would you share the details about making use of the remain bits in the
replicaiton field?
Sure. The HeaderFormat is a 64-bit long and its layout is {{[4-bit
storagePolicyID][1-bit isStriped][11-bit replication][48-bit
preferredBlockSize]}}. The patch doesn't change the layout -- it just uses the
11-bit replication to store the policy ID. Therefore it can support up to
{{2^11-1=2047}} different policies. I think that'll be enough for all the
combinations of codecs, cell sizes and layouts.
bq. do we add/have tests to test multiple policies can work at the same time in
a cluster
Good point. I'll add a test to cover this.
> Erasure coding: NameNode manages EC schemas
> -------------------------------------------
>
> 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
>
>
> 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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