hadoop/hadoop-ozone/docs/content/Settings.md

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title: Configuration
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If you are feeling adventurous, you can setup ozone in a real cluster.
Setting up a real cluster requires us to understand the components of Ozone.
Ozone is designed to work concurrently with HDFS. However, Ozone is also
capable of running independently. The components of ozone are the same in both approaches.
## Ozone Components
1. Ozone Manager - Is the server that is in charge of the namespace of Ozone. Ozone Manager is responsible for all volume, bucket and key operations.
2. Storage Container Manager - Acts as the block manager. Ozone Manager
requests blocks from SCM, to which clients can write data.
3. Datanodes - Ozone data node code runs inside the HDFS datanode or in the independent deployment case runs an ozone datanode daemon.
## Setting up an Ozone only cluster
* Please untar the ozone-0.2.1-SNAPSHOT to the directory where you are going
to run Ozone from. We need Ozone jars on all machines in the cluster. So you
need to do this on all machines in the cluster.
* Ozone relies on a configuration file called ```ozone-site.xml```. To
generate a template that you can replace with proper values, please run the
following command. This will generate a template called ```ozone-site.xml``` at
the specified path (directory).
{{< highlight bash >}}
ozone genconf -output <path>
{{< /highlight >}}
Let us look at the settings inside the generated file (ozone-site.xml) and
how they control ozone. Once the right values are defined, this file
needs to be copied to ```ozone directory/etc/Hadoop```.
* **ozone.enabled** This is the most critical setting for ozone.
Ozone is a work in progress and users have to enable this service explicitly.
By default, Ozone is disabled. Setting this flag to `true` enables ozone in the
HDFS or Ozone cluster.
Here is an example,
{{< highlight xml >}}
<property>
<name>ozone.enabled</name>
<value>True</value>
</property>
{{< /highlight >}}
* **ozone.metadata.dirs** Allows Administrators to specify where the
metadata must reside. Usually you pick your fastest disk (SSD if
you have them on your nodes). OzoneManager, SCM and datanode will write the
metadata to this path. This is a required setting, if this is missing Ozone
will fail to come up.
Here is an example,
{{< highlight xml >}}
<property>
<name>ozone.metadata.dirs</name>
<value>/data/disk1/meta</value>
</property>
{{< /highlight >}}
* **ozone.scm.names** Storage container manager(SCM) is a distributed block
service which is used by ozone. This property allows data nodes to discover
SCM's address. Data nodes send heartbeat to SCM.
Until HA feature is complete, we configure ozone.scm.names to be a
single machine.
Here is an example,
{{< highlight xml >}}
<property>
<name>ozone.scm.names</name>
<value>scm.hadoop.apache.org</value>
</property>
{{< /highlight >}}
* **ozone.scm.datanode.id** Data nodes generate a Unique ID called Datanode
ID. This identity is written to the file specified by this path. *Data nodes
will create this path if it doesn't exist already.*
Here is an example,
{{< highlight xml >}}
<property>
<name>ozone.scm.datanode.id</name>
<value>/data/disk1/meta/node/datanode.id</value>
</property>
{{< /highlight >}}
* **ozone.om.address** OM server address. This is used by OzoneClient and
Ozone File System.
Here is an example,
{{< highlight xml >}}
<property>
<name>ozone.om.address</name>
<value>ozonemanager.hadoop.apache.org</value>
</property>
{{< /highlight >}}
### Ozone Settings Summary
| Setting | Value | Comment |
|--------------------------------|------------------------------|------------------------------------------------------------------|
| ozone.enabled | true | This enables SCM and containers in HDFS cluster. |
| ozone.metadata.dirs | file path | The metadata will be stored here. |
| ozone.scm.names | SCM server name | Hostname:port or IP:port address of SCM. |
| ozone.scm.block.client.address | SCM server name and port | Used by services like OM |
| ozone.scm.client.address | SCM server name and port | Used by client-side |
| ozone.scm.datanode.address | SCM server name and port | Used by datanode to talk to SCM |
| ozone.om.address | OM server name | Used by Ozone handler and Ozone file system. |