Siyao Meng created HDDS-17113:
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Summary: SCM to prefer a Ratis pipeline on the writer's datanode
when allocating blocks
Key: HDDS-17113
URL: https://issues.apache.org/jira/browse/HDDS-17113
Project: Apache Ozone
Issue Type: Improvement
Reporter: Siyao Meng
When a client runs on a datanode host (for example an HBase RegionServer
colocated with a datanode), Ratis block allocation ignores the client's
location, so none of the pipeline's datanodes may be local to the writer. HDFS
places the first replica on the writer's datanode, which lets later reads of
that data (e.g. HBase compactions) use short-circuit reads.
Proposal: add {{hdds.scm.block.allocation.prefer.client.local}} (default
{{false}}). When set, OM passes the client address to SCM on every block
allocation, and SCM first tries open Ratis pipelines led by the client's
datanode, then other open pipelines that contain it, before falling back to the
pipeline choose policy. A pipeline led by the client's datanode also keeps the
client to leader hop of every write on the same host, which is the colocation
discussed in HDDS-11000.
EC allocation is unchanged.
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