ChenSammi commented on code in PR #8528:
URL: https://github.com/apache/ozone/pull/8528#discussion_r2128138829
##########
hadoop-hdds/docs/content/feature/Topology.md:
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@@ -23,86 +23,190 @@ summary: Configuration for rack-awarness for improved
read/write
limitations under the License.
-->
-Ozone can use topology related information (for example rack placement) to
optimize read and write pipelines. To get full rack-aware cluster, Ozone
requires three different configuration.
-
- 1. The topology information should be configured by Ozone.
- 2. Topology related information should be used when Ozone chooses 3 different
datanodes for a specific pipeline/container. (WRITE)
- 3. When Ozone reads a Key it should prefer to read from the closest node.
-
-<div class="alert alert-warning" role="alert">
-
-Ozone uses RAFT replication for Open containers (write), and an async
replication for closed, immutable containers (cold data). As RAFT requires
low-latency network, topology awareness placement is available only for closed
containers. See the [page about Containers]({{< ref "concept/Containers.md">}})
about more information related to Open vs Closed containers.
-
-</div>
-
-## Topology hierarchy
-
-Topology hierarchy can be configured with using
`net.topology.node.switch.mapping.impl` configuration key. This configuration
should define an implementation of the
`org.apache.hadoop.net.CachedDNSToSwitchMapping`. As this is a Hadoop class,
the configuration is exactly the same as the Hadoop Configuration
-
-### Static list
-
-Static list can be configured with the help of ```TableMapping```:
-
-```XML
+Apache Ozone uses topology information (e.g., rack placement) to optimize data
access and improve resilience. A fully rack-aware cluster needs:
+
+1. Configured network topology.
+2. Topology-aware DataNode selection for container replica placement (write
path).
+3. Prioritized reads from topologically closest DataNodes (read path).
+
+## Applicability to Container Types
+
+Ozone's topology-aware placement strategies vary by container replication type
and state:
+
+* **RATIS Replicated Containers:** Ozone uses RAFT replication for Open
containers (write), and an async replication for closed, immutable containers
(cold data). As RAFT requires low-latency network, topology awareness placement
is available only for closed containers. See the [page about
Containers](concept/Containers.md) about more information related to Open vs
Closed containers.
+* **Erasure Coded (EC) Containers:** EC demands topology awareness from the
initial write. For an EC key, OM allocates a block group of `$d+p$` distinct
DataNodes selected by SCM's `ECPipelineProvider` to ensure rack diversity and
fault tolerance. This topology-aware selection is integral to the EC write path
for new blocks. \[2]
+
+## Configuring Topology Hierarchy
+
+Ozone determines DataNode network locations (e.g., racks) using Hadoop's rack
awareness, configured via `net.topology.node.switch.mapping.impl` in
`core-site.xml`. This key specifies a
`org.apache.hadoop.net.CachedDNSToSwitchMapping` implementation. \[1]
Review Comment:
Ozone doesn't mandatory requires core-site.xml. So maybe "ozone-site.xml" is
more appropriate here.
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