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https://issues.apache.org/jira/browse/HDFS-6685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14079374#comment-14079374
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Tsz Wo Nicholas Sze commented on HDFS-6685:
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> ... But I haven't seen this condition while matching the targets for movement
> ...
It is in isGoodBlockCandidate(..)
{code}
private boolean isGoodBlockCandidate(Source source,
- BalancerDatanode target, BalancerBlock block) {
+ BalancerDatanode.StorageGroup target, BalancerBlock block) {
+ if (source.storageType != target.storageType) {
+ return false;
+ }
...
{code}
> ... Here r is not used. I feel this and related changes can be removed.
Good catch. I forgot to remove it after simplified the calculation.
> Balancer should preserve storage type of replicas
> -------------------------------------------------
>
> Key: HDFS-6685
> URL: https://issues.apache.org/jira/browse/HDFS-6685
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: balancer
> Reporter: Tsz Wo Nicholas Sze
> Assignee: Tsz Wo Nicholas Sze
> Attachments: h6685_20140728.patch, h6685_20140729.patch,
> h6685_20140730.patch
>
>
> When Balancer moves replicas to balance the cluster, it should always move
> replicas from a storage with any type to another storage with the same type,
> i.e. it preserves storage type of replicas. It does not make sense to move
> replicas to a different storage type.
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