ChenSammi commented on code in PR #8641: URL: https://github.com/apache/ozone/pull/8641#discussion_r2157968777
########## hadoop-hdds/docs/content/feature/multi-raft-support.md: ########## @@ -0,0 +1,86 @@ +--- +title: "Multi-Raft Support in Ozone" +menu: + main: + parent: Features +summary: "Enables each DataNode to participate in multiple Ratis pipelines concurrently to improve resource utilization and write throughput." +--- +<!--- + Licensed to the Apache Software Foundation (ASF) under one or more + contributor license agreements. See the NOTICE file distributed with + this work for additional information regarding copyright ownership. + The ASF licenses this file to You under the Apache License, Version 2.0 + (the "License"); you may not use this file except in compliance with + the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. +--> + +## Overview +The early Ozone versions supported one Raft pipeline per DataNode, which meant each DataNode could only participate in one Ratis replication group (pipeline) at a time. This limited its concurrent write handling capacity for replicated data and could lead to under-utilization of resources. + +Multi-Raft support allows a DataNode to be part of multiple Ratis pipelines at once, +improving write throughput and ensuring better utilization of disk and network resources. +This is particularly useful when DataNodes have multiple disks. + +## Prerequisites +- Ozone 0.5.0 or later +- Replication type: RATIS +- Multiple metadata volumes on each DataNode (via `hdds.container.ratis.datanode.storage.dir`) +- Adequate CPU, memory, and network bandwidth + +## How It Works +SCM can now create overlapping pipelines: each DataNode can join multiple Raft groups, up to a configurable limit. This boosts concurrency and avoids idle nodes. Raft logs are stored separately on different metadata volumes to reduce disk contention. Ratis handles concurrent logs per node. + +## How to Use +1. Configure DataNode metadata volumes: + ```xml + <property> + <name>hdds.container.ratis.datanode.storage.dir</name> + <value>/disk1/ratis,/disk2/ratis</value> + </property> + ``` +2. Set pipeline limits in `ozone-site.xml`: + ```xml + <property> + <name>ozone.scm.datanode.pipeline.limit</name> + <value>0</value> + </property> + <property> + <name>ozone.scm.pipeline.per.metadata.disk</name> + <value>2</value> + </property> + ``` +3. Restart SCM and DataNodes. +4. Validate with: + ```bash + ozone admin pipeline list + ozone admin datanode list + ``` + +## Configuration +- `ozone.scm.datanode.pipeline.limit` (default: 2) + - Set to `0` to auto-compute based on metadata volumes Review Comment: Can we have this auto-compute logic explained here? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@ozone.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@ozone.apache.org For additional commands, e-mail: issues-h...@ozone.apache.org
