[
https://issues.apache.org/jira/browse/HDFS-7613?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14349914#comment-14349914
]
Walter Su commented on HDFS-7613:
---------------------------------
I'm a little confused about how FSNamesystem should call BlockPlacementPolicy
when a file is striped. I looked into HDFS-7339-008.patch, I saw:
+ numTargets = isStriped ?
+ HdfsConstants.NUM_DATA_BLOCKS + HdfsConstants.NUM_PARITY_BLOCKS :
+ pendingFile.getFileReplication();
final DatanodeStorageInfo targets[] =
getBlockManager().chooseTarget4NewBlock(
- src, replication, clientNode, excludedNodes, blockSize, favoredNodes,
+ src, numTargets, clientNode, excludedNodes, blockSize, favoredNodes,
storagePolicyID);
from the above code, I got: FSNamesystem call BlockPlacementPolicy.chooseTarget
one time, and BlockPlacementPolicy returns all blocks' locations for the
blockgroup. BlockPlacementPolicy returns blocks' locations but not replicas'.
It's a matter of how we are thinking of second arguments. If we treat it as
blocks' locations for many blocks, it's blocks' locations. If we treat it as
replicas' locations for one block, then it is.
I'll implement the BlockPlacementPolicyFaultTolerant for EC. And I think
BlockPlacementPolicyFaultTolerant can also work in non-EC situation.
> Block placement policy for erasure coding groups
> ------------------------------------------------
>
> Key: HDFS-7613
> URL: https://issues.apache.org/jira/browse/HDFS-7613
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Zhe Zhang
> Assignee: Walter Su
>
> Blocks in an erasure coding group should be placed in different failure
> domains -- different DataNodes at the minimum, and different racks ideally.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
