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https://issues.apache.org/jira/browse/HDFS-7866?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15075676#comment-15075676
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Rui Li commented on HDFS-7866:
------------------------------
Thanks [~drankye] for the review!
1. Sure, will do.
2. Since the system policies are static members, they'll have the same ID after
NN restarts. But I agree it's better not to let {{ErasureCodingPolicy}}
generate the ID itself. How about pass the ID to it as a constructor parameter,
and have the ID generator in {{ErasureCodingPolicyManager}}?
3. Currently striped files all have 0 as the replication factor. E.g. in the
INodeFile part of the patch:
{code}
- // Replication factor for striped files is zero
+ // For erasure coded files, replication is used to store ec policy id
+ if (isStriped) {
+ Preconditions.checkArgument(replication >= 0);
+ }
+ h = REPLICATION.BITS.combine(replication, h);
if (isStriped) {
- h = REPLICATION.BITS.combine(0L, h);
h = IS_STRIPED.BITS.combine(1L, h);
} else {
- h = REPLICATION.BITS.combine(replication, h);
h = IS_STRIPED.BITS.combine(0L, h);
}
{code}
With the patch, striped file's replication factor is actually the policy ID.
The modification you mentioned in {{HdfsFileStatus}} is to avoid confusing
users by displaying policy ID as replication factor.
4. {{QUEUE_VERY_UNDER_REPLICATED}} means the current redundancy is 1/3 of
desired redundancy. So I changed the comment to be consistent with the code.
You can refer to discussions in HDFS-8461.
5. Which map do you think we should keep?
> 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, 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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